CipA is the primary cellulosomal scaffoldin protein in Acetivibrio thermocellus (formerly Clostridium thermocellum). It is a large (1853 aa) non-catalytic structural protein that serves as the central organizing scaffold of the cellulosome - a supramolecular multi-enzyme complex that efficiently degrades plant cell wall polysaccharides. CipA contains nine type I cohesin domains that bind dockerin-bearing catalytic enzymes (cellulases, hemicellulases), a central CBM3a carbohydrate-binding module that targets the complex to crystalline cellulose, and a C-terminal type II dockerin (with associated X module) that anchors the cellulosome to cell-surface proteins bearing type II cohesins (SdbA, OlpB, Orf2p). CipA does NOT possess any catalytic/enzymatic activity - its function is purely structural and organizational, bringing multiple enzymes into proximity for synergistic cellulose degradation.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0000272
polysaccharide catabolic process
|
IEA
GO_REF:0000120 |
KEEP AS NON CORE |
Summary: CipA is involved in polysaccharide catabolism but only indirectly through its scaffolding role. CipA itself has no catalytic activity; it organizes dockerin-bearing enzymes that perform the actual hydrolysis. The annotation captures participation in the process but overstates direct involvement.
Reason: While CipA is essential for efficient polysaccharide degradation by the cellulosome, it is not directly involved in the catabolic process itself. CipA is a non-catalytic structural organizer that assembles multiple cellulases and hemicellulases into a multienzyme complex. The scaffoldin promotes enzyme synergy but does not catalyze any reactions. This annotation is acceptable as a secondary/non-core function reflecting its organizational role in the process.
Supporting Evidence:
file:ACET2/cipA/cipA-deep-research-falcon.md
CipA is a non-catalytic structural organizer that assembles multiple cellulases and hemicellulases into a multienzyme complex through high-affinity type I cohesin-dockerin interactions
|
|
GO:0004553
hydrolase activity, hydrolyzing O-glycosyl compounds
|
IEA
GO_REF:0000002 |
REMOVE |
Summary: This annotation is INCORRECT. CipA has no hydrolase activity whatsoever. It is a non-catalytic scaffoldin protein that organizes enzymes but does not itself possess any enzymatic function. This appears to be an erroneous transfer from the dockerin domain (IPR002105), which is also present in catalytic cellulosomal enzymes.
Reason: CipA is explicitly described in the literature as a non-catalytic scaffolding glycoprotein (UniProt CC-FUNCTION). The UniProt function annotation states that CipA acts as a scaffolding protein in the cellulosome and promotes binding of cellulose to the catalytic domains of the cellulolytic enzymes - note it promotes binding TO catalytic domains, it does not have catalytic activity itself. The deep research confirms CipA is a non-catalytic structural organizer (cipA-deep-research-falcon.md). The InterPro domain IPR002105 (Dockerin_1_rpt) is present in both scaffoldins and catalytic enzymes; the hydrolase activity annotation was incorrectly transferred because dockerins are commonly found in hydrolases, but the scaffoldin CipA only uses its dockerin (type II) for anchoring to cell-surface proteins, not for catalysis. This is a clear over-annotation error.
Supporting Evidence:
file:ACET2/cipA/cipA-deep-research-falcon.md
CipA is a non-catalytic structural organizer that assembles multiple cellulases and hemicellulases into a multienzyme complex
|
|
GO:0005576
extracellular region
|
IEA
GO_REF:0000044 |
ACCEPT |
Summary: This annotation is correct. CipA is a secreted protein that functions in the extracellular space, either cell-surface anchored or as part of cell-free cellulosomes.
Reason: UniProt explicitly states that CipA is secreted and remains at the cell surface. The deep research confirms that CipA-enabled cellulosomes are predominantly cell surface-associated through anchoring scaffoldins bearing SLH domains. C. thermocellum also produces cell-free (diffusible) cellulosomes that operate at a distance from the bacterial surface. The protein has a signal peptide (residues 1-28) and functions extracellularly.
Supporting Evidence:
file:ACET2/cipA/cipA-deep-research-falcon.md
CipA-enabled cellulosomes are predominantly cell surface-associated through anchoring scaffoldins bearing SLH domains. C. thermocellum also produces cell-free (diffusible) cellulosomes that operate at a distance from the bacterial surface
|
|
GO:0005975
carbohydrate metabolic process
|
IEA
GO_REF:0000002 |
MODIFY |
Summary: This annotation is too general and misrepresents CipA's role. CipA does not metabolize carbohydrates; it organizes enzymes that do. This is an overly broad annotation derived from the CBM3 domain.
Reason: CipA's CBM3a domain binds cellulose but does not metabolize it. The protein's role is structural - organizing the cellulosome for efficient carbohydrate degradation. A more appropriate annotation would be GO:0044575 (cellulosome assembly) which captures the actual biological process CipA participates in. The annotation to carbohydrate metabolic process incorrectly implies direct metabolic activity.
Proposed replacements:
cellulosome assembly
Supporting Evidence:
file:ACET2/cipA/cipA-deep-research-falcon.md
CBM3a function: targets crystalline cellulose to increase local enzyme concentration and synergize hydrolysis; CBM3a is the prevalent cellulosomal CBM in C. thermocellum
|
|
GO:0030245
cellulose catabolic process
|
IEA
GO_REF:0000043 |
KEEP AS NON CORE |
Summary: Similar to GO:0000272, this annotation captures CipA's indirect involvement in cellulose degradation through its scaffolding function but overstates direct participation in the catabolic process.
Reason: CipA is essential for efficient cellulose catabolism via the cellulosome, but it does not itself degrade cellulose. Its CBM3a module targets the complex to cellulose substrate, and its cohesins organize the catalytic enzymes that perform hydrolysis. The annotation reflects involvement in the process but should be considered non-core since CipA's primary function is structural organization (cellulosome assembly) rather than direct catalysis.
Supporting Evidence:
file:ACET2/cipA/cipA-deep-research-falcon.md
CipA is essential for high-efficiency cellulose deconstruction, functioning at the interface of enzyme synergy, substrate targeting, and cell-surface attachment
|
|
GO:0030246
carbohydrate binding
|
IEA
GO_REF:0000002 |
ACCEPT |
Summary: This annotation is correct but could be made more specific. CipA binds carbohydrates via its CBM3a domain, specifically binding crystalline cellulose.
Reason: CipA contains a well-characterized CBM3a (carbohydrate-binding module family 3a) domain at positions 365-523. The deep research confirms that CBM3a targets crystalline cellulose to increase local enzyme concentration and synergize hydrolysis. CBM3a is the prevalent cellulosomal CBM in C. thermocellum (cipA-deep-research-falcon.md). The crystal structure of this domain has been solved (PDB: 1NBC at 1.75 A resolution). This is a core molecular function.
Supporting Evidence:
file:ACET2/cipA/cipA-deep-research-falcon.md
CBM3a function: targets crystalline cellulose to increase local enzyme concentration and synergize hydrolysis
|
|
GO:0030248
cellulose binding
|
IEA
GO_REF:0000002 |
ACCEPT |
Summary: This annotation is correct and represents a core molecular function of CipA. The CBM3a domain specifically binds crystalline cellulose.
Reason: CipA's CBM3a domain (residues 365-523) specifically binds crystalline cellulose, targeting the cellulosome to its substrate. This is experimentally verified through structural studies - the crystal structure of the CBM3a domain was solved at 1.75 A resolution (PDB: 1NBC; Tormo et al., EMBO J 1996). The deep research states that CBM3a function targets crystalline cellulose to increase local enzyme concentration and synergize hydrolysis (cipA-deep-research-falcon.md). This is a core function of CipA - without cellulose binding, the cellulosome cannot target its substrate.
Supporting Evidence:
file:ACET2/cipA/cipA-deep-research-falcon.md
CBM3a function: targets crystalline cellulose to increase local enzyme concentration and synergize hydrolysis
|
|
GO:0071555
cell wall organization
|
IEA
GO_REF:0000043 |
REMOVE |
Summary: This annotation is misleading. CipA is involved in PLANT cell wall DEGRADATION (as a target substrate), not in bacterial cell wall organization. The UniProt keyword mapping appears to have conflated cell wall degradation with cell wall organization.
Reason: CipA functions in the degradation of plant cell walls (cellulose, hemicellulose), not in organizing the bacterial cell wall. While CipA is anchored at the cell surface, its function is to organize the cellulosome for degrading extracellular plant material, not to organize the bacterium's own cell wall. The UniProt keywords include Cell wall biogenesis/degradation which likely triggered this annotation, but the context is substrate degradation, not endogenous cell wall organization. This is a semantic error in the automated annotation pipeline.
Supporting Evidence:
file:ACET2/cipA/cipA-deep-research-falcon.md
CipA's modular architecture orchestrates assembly of numerous dockerin-bearing CAZymes and anchors the complex to the cell surface through SLH-bearing secondary scaffoldins
|
|
GO:0005515
protein binding
|
IPI
PMID:14623971 Cellulosome assembly revealed by the crystal structure of th... |
MODIFY |
Summary: This annotation is experimentally supported but should be made more specific. PMID:14623971 reports the crystal structure of the cohesin-dockerin complex, demonstrating that CipA's cohesin domains bind dockerin domains on enzymes.
Reason: The IPI annotation from PMID:14623971 is based on the crystal structure of the type I cohesin-dockerin complex from C. thermocellum (WITH: UniProtKB:P51584, XynY xylanase). The study demonstrates that the beta-sheet cohesin domain interacts predominantly with one of the helices of the dockerin (PMID:14623971). However, protein binding is too vague. CipA specifically binds type I dockerin domains through its nine type I cohesin modules. The annotation should be changed to GO:1990308 (type-I dockerin domain binding) which precisely describes this molecular function.
Proposed replacements:
type-I dockerin domain binding
Supporting Evidence:
PMID:14623971
The data show that the beta-sheet cohesin domain interacts predominantly with one of the helices of the dockerin.
|
|
GO:0005515
protein binding
|
IPI
PMID:16384918 Mechanism of bacterial cell-surface attachment revealed by t... |
MODIFY |
Summary: This annotation documents CipA's C-terminal type II dockerin binding to type II cohesins on cell-surface anchoring proteins. The interaction demonstrated is between CipA's X-DocII module and a type II cohesin from Cthe_1307.
Reason: PMID:16384918 reports the structure of the type II cohesin-dockerin complex involving CipA's C-terminal X-dockerin module (WITH: UniProtKB:A3DF10, Cthe_1307). The study describes an ultra-high-affinity complex between type II Doc together with its neighboring X module from the cellulosome scaffold of Clostridium thermocellum and a type II Coh module associated with the bacterial cell surface. The annotation should be more specific: GO:1990312 (type-II cohesin domain binding) captures that CipA's dockerin binds to type II cohesins.
Proposed replacements:
type-II cohesin domain binding
Supporting Evidence:
PMID:16384918
Here, we report the structure of an ultra-high-affinity (K(a) = 1.44 x 10(10) M(-1)) complex between type II Doc, together with its neighboring X module from the cellulosome scaffold of Clostridium thermocellum, and a type II Coh module associated with the bacterial cell surface.
|
|
GO:0005515
protein binding
|
IPI
PMID:17360613 Evidence for a dual binding mode of dockerin modules to cohe... |
MODIFY |
Summary: This annotation provides additional evidence for CipA's cohesin-dockerin interactions, demonstrating a dual binding mode where dockerins can interact with cohesins in two orientations.
Reason: PMID:17360613 provides structural evidence for the dual binding mode of type I dockerins to type I cohesins. The study shows that both repeats could interact with cohesins by a common mechanism and that dockerins can bind in a 180-degree rotated orientation (PMID:17360613). This further characterizes the type I cohesin-dockerin interaction. As with PMID:14623971, the annotation should be made more specific to GO:1990308 (type-I dockerin domain binding).
Proposed replacements:
type-I dockerin domain binding
Supporting Evidence:
PMID:17360613
The dual binding mode is predicted to impart significant plasticity into the orientation of the catalytic subunits within this supramolecular assembly
|
|
GO:0043263
cellulosome
|
IDA
PMID:14623971 Cellulosome assembly revealed by the crystal structure of th... |
NEW |
Summary: CipA is the primary structural component of the cellulosome. This cellular component annotation is essential and missing from the current annotation set.
Reason: CipA is THE primary scaffoldin of the C. thermocellum cellulosome - it IS the cellulosome scaffold. UniProt names it Cellulosomal-scaffolding protein A and states it acts as a scaffolding protein in the cellulosome. The deep research confirms that cipA encodes the primary cellulosomal scaffoldin in Clostridium thermocellum (cipA-deep-research-falcon.md). This CC annotation is critical for understanding CipA's identity and should be added with IDA evidence based on direct characterization studies.
Supporting Evidence:
PMID:14623971
This megadalton catalytic machine organizes an enzymatic consortium on a multifaceted molecular scaffold
|
|
GO:0044575
cellulosome assembly
|
IDA
PMID:14623971 Cellulosome assembly revealed by the crystal structure of th... |
NEW |
Summary: CipA's primary biological process is assembling the cellulosome by recruiting dockerin-bearing enzymes. This is a core function that should be annotated.
Reason: CipA's nine type I cohesin domains bind dockerin-bearing enzymes, directly assembling the cellulosome complex. PMID:14623971 reveals the structure of the cohesin-dockerin complex from Clostridium thermocellum showing how cellulosome assembly occurs. The deep research states that CipA is a non-catalytic structural organizer that assembles multiple cellulases and hemicellulases into a multienzyme complex through high-affinity type I cohesin-dockerin interactions (cipA-deep-research-falcon.md). This is CipA's primary biological process.
Supporting Evidence:
PMID:14623971
This megadalton catalytic machine organizes an enzymatic consortium on a multifaceted molecular scaffold whose "cohesin" domains interact with corresponding "dockerin" domains of the enzymes.
|
|
GO:0005198
structural molecule activity
|
IDA
PMID:14623971 Cellulosome assembly revealed by the crystal structure of th... |
NEW |
Summary: CipA provides the structural framework of the cellulosome. This molecular function annotation captures its non-catalytic scaffolding role.
Reason: CipA contributes to the structural integrity of the cellulosome complex. It is explicitly described as a non-catalytic scaffolding glycoprotein that provides the structural backbone for enzyme assembly. Unlike catalytic cellulosomal components, CipA's molecular function is purely structural - organizing and maintaining the multi-enzyme complex. This annotation appropriately captures that CipA's molecular function is structural organization rather than catalysis.
Supporting Evidence:
PMID:14623971
This megadalton catalytic machine organizes an enzymatic consortium on a multifaceted molecular scaffold
|
Q: Are there conditions under which CipA might directly participate in carbohydrate modification or processing beyond its scaffolding role?
Experiment: Comprehensive interactome analysis of CipA cohesin domains to quantify the full repertoire of dockerin-bearing proteins recruited to the cellulosome in vivo.
Hypothesis: While the cohesin-dockerin interaction is well-characterized structurally, the complete set of CipA interaction partners in vivo remains incompletely defined.
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organism: ACET2
gene_id: cipA
gene_symbol: cipA
uniprot_accession: Q06851
protein_description: 'RecName: Full=Cellulosomal-scaffolding protein A; AltName:
Full=Cellulose-integrating protein A; AltName: Full=Cellulosomal glycoprotein
S1/SL; AltName: Full=Cohesin; Flags: Precursor;'
gene_info: Name=cipA; OrderedLocusNames=Cthe_3077;
organism_full: Acetivibrio thermocellus (strain ATCC 27405 / DSM 1237 / JCM 9322
/ NBRC 103400 / NCIMB 10682 / NRRL B-4536 / VPI 7372) (Clostridium thermocellum).
protein_family: Not specified in UniProt
protein_domains: CarboxyPept-like_regulatory. (IPR008969); CBM2/CBM3_carb-bd_dom_sf.
(IPR008965); CBM3. (IPR001956); CBM3_sf. (IPR036966); Cohesin_dom. (IPR002102)
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BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.
DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'cipA' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information
Please provide a comprehensive research report on the gene cipA (gene ID: cipA, UniProt: Q06851) in ACET2.
The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
Question: You are an expert researcher providing comprehensive, well-cited information.
Provide detailed information focusing on:
1. Key concepts and definitions with current understanding
2. Recent developments and latest research (prioritize 2023-2024 sources)
3. Current applications and real-world implementations
4. Expert opinions and analysis from authoritative sources
5. Relevant statistics and data from recent studies
Format as a comprehensive research report with proper citations. Include URLs and publication dates where available.
Always prioritize recent, authoritative sources and provide specific citations for all major claims.
BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.
DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'cipA' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information
Please provide a comprehensive research report on the gene cipA (gene ID: cipA, UniProt: Q06851) in ACET2.
The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
Plan status: Objectives verified and evidence gathered from primary and recent literature. Below is a comprehensive, cited research report on cipA (Cthe_3077; UniProt Q06851) from Acetivibrio thermocellus (Clostridium thermocellum), including identity verification, functional annotation, domain architecture, localization, roles in cellulose degradation, recent developments, applications, expert analysis, and quantitative data.
Comprehensive research report: cipA (Cthe_3077; UniProt Q06851) in Acetivibrio thermocellus
Identity verification and nomenclature
- Gene/protein identity: cipA encodes the primary cellulosomal scaffoldin (often termed “CipA”) in Clostridium thermocellum (synonym: Acetivibrio thermocellus), locus Cthe_3077. Classical and mechanistic literature consistently identifies CipA as the main non-catalytic scaffoldin of the C. thermocellum cellulosome, organizing dockerin-bearing enzymes into a multienzyme complex and linking the complex to the cell surface via anchoring scaffoldins (SdbA/OlpB/Orf2p). This aligns with UniProt Q06851 annotations. (pinheiro2010novelinsightinto pages 47-50, pinheiro2009functionalinsightsinto pages 1-4)
Key concepts, definitions, and current understanding
- Cellulosome: a supramolecular multi-enzyme complex that deconstructs plant cell wall polysaccharides. In C. thermocellum, the primary scaffoldin CipA contains multiple type I cohesins that bind enzymatic subunits carrying type I dockerins, a cellulose-targeting CBM3a, and a C-terminal X–dockerin module (type II) that binds anchoring scaffoldins bearing type II cohesins. (pinheiro2010novelinsightinto pages 47-50, pinheiro2010novelinsightinto pages 37-40)
- Cohesin–dockerin specificity: Type I cohesins on CipA bind type I dockerins on catalytic subunits; the C-terminal type II dockerin (on CipA’s X–Doc dyad) binds type II cohesins on anchoring scaffoldins (no cross-specificity between types I and II). Coh–Doc interactions are Ca2+-dependent and among the strongest non-covalent protein–protein interactions; dockerins carry duplicated EF-hand-like Ca2+-binding motifs and can support dual-binding modes, though stoichiometry is 1:1. (pinheiro2010novelinsightinto pages 47-50, santos2025unconventionalcohesindockerinbinding pages 46-49, pinheiro2010novelinsightinto pages 40-42)
- Central role of CipA: Genetic and systems studies demonstrate that the primary scaffoldin CipA is essential for high-efficiency cellulose degradation in C. thermocellum; secondary scaffoldins contribute but are less critical. C. thermocellum deploys both cell-bound and cell-free cellulosomes. Science Advances (2016) provides a detailed systems analysis with functional deletion evidence. URL: https://doi.org/10.1126/sciadv.1501254 (Feb 2016). (xu2016dramaticperformanceof pages 1-2)
Protein architecture and domains (alignment with UniProt/IPR domains)
- Domain map: 2 CohI – CBM3a – 7 CohI – X–DocII, totaling nine type I cohesins with a central family 3a CBM and C-terminal X–dockerin (type II). This corroborates the reported modular architecture and the presence of CBM3/CBM3_sf and cohesin domains. (pinheiro2010novelinsightinto pages 37-40, pinheiro2010novelinsightinto pages 47-50)
- CBM3a function: targets crystalline cellulose to increase local enzyme concentration and synergize hydrolysis; CBM3a is the prevalent cellulosomal CBM in C. thermocellum. (pinheiro2010novelinsightinto pages 47-50, xu2016dramaticperformanceof pages 1-2)
- Cohesins and dockerins: nine type I cohesins on CipA integrate numerous dockerin-bearing CAZymes; dockerins are ~70 aa with duplicated segments yielding two potential binding interfaces and Ca2+ dependence. (pinheiro2010novelinsightinto pages 47-50, pinheiro2009functionalinsightsinto pages 7-9, santos2025unconventionalcohesindockerinbinding pages 46-49, pinheiro2010novelinsightinto pages 40-42)
- Anchoring via X–DocII and SLH-bearing partners: CipA’s X–DocII binds type II cohesins on anchoring scaffoldins (e.g., SdbA, OlpB, Orf2p), which tether the complex to the cell wall through surface-layer homology (SLH) modules. (pinheiro2010novelinsightinto pages 37-40, pinheiro2010novelinsightinto pages 47-50, pinheiro2009functionalinsightsinto pages 7-9)
| Feature | Description | Evidence (citation IDs) |
|---|---|---|
| Protein identity / organism | CipA (gene cipA; locus Cthe_3077) — primary scaffoldin from Clostridium thermocellum (syn. Acetivibrio thermocellus). | (pinheiro2010novelinsightinto pages 47-50, pinheiro2009functionalinsightsinto pages 1-4) |
| Primary role | Organizes the cellulosome by anchoring dockerin-bearing enzymatic subunits (type I Coh–Doc) and linking to anchoring scaffoldins via C-terminal X–Doc/type II interactions. | (xu2016dramaticperformanceof pages 1-2, pinheiro2010novelinsightinto pages 47-50) |
| Domain map (reported) | Modular architecture reported as 2 CohI – CBM3a – 7 CohI – X–DocII (total nine type I cohesins, central CBM3a, C-terminal X–Doc/type II). | (pinheiro2010novelinsightinto pages 37-40, pinheiro2010novelinsightinto pages 47-50) |
| Number and type of cohesins | Nine type I cohesin modules (type I Coh) distributed along the scaffoldin. | (pinheiro2010novelinsightinto pages 47-50, pinheiro2009functionalinsightsinto pages 7-9) |
| CBM3a function | Family 3a carbohydrate-binding module that binds crystalline cellulose, targeting the cellulosome to substrate and increasing local enzyme concentration. | (pinheiro2010novelinsightinto pages 47-50, xu2016dramaticperformanceof pages 1-2) |
| X–DocII function & anchoring partners | C-terminal X–dockerin (type II) mediates binding to type II cohesins on anchoring scaffoldins (e.g., SdbA, OlpB, Orf2p) which are cell-surface associated (SLH-bearing). | (pinheiro2010novelinsightinto pages 47-50, pinheiro2010novelinsightinto pages 37-40) |
| CohI–DocI binding properties | Cohesin–dockerin interactions are very strong noncovalent bonds, Ca2+-dependent; dockerins have duplicated Ca2+-binding motifs and can permit dual-binding (180°) modes though stoichiometry is 1:1. | (santos2025unconventionalcohesindockerinbinding pages 46-49, pinheiro2010novelinsightinto pages 40-42) |
| Localization | Primarily cell-surface anchored via SLH-bearing secondary scaffoldins (OlpA/OlpB/SdbA/Orf2p) but also participates in cell-free (diffusible) cellulosomes. | (pinheiro2009functionalinsightsinto pages 7-9, xu2016dramaticperformanceof pages 1-2) |
| Quantitative system context | C. thermocellum encodes ~72 dockerin-containing cellulosomal proteins (plus additional free enzymes); CipA is central to assembly and activity. | (xu2016dramaticperformanceof pages 1-2, pinheiro2009functionalinsightsinto pages 1-4) |
| Recent (2023–2024) applications & engineering | Recent reviews and studies describe designer cellulosomes, scaffold/cohesin engineering, CBM-enabled material functionalization, and modular scaffold approaches for immobilization and enhanced hydrolysis. | (li2024harnessingcellulosebindingprotein pages 10-10, lindic2025structuralandfunctional pages 4-5, lindic2025structuralandfunctional pages 19-20) |
Table: Concise table summarizing CipA (Cthe_3077) domain architecture, roles, localization, system context, and recent 2023–2024 application-relevant literature with evidence citations.
Primary function, pathway context, and localization
- Function: CipA is a non-catalytic structural organizer that assembles multiple cellulases and hemicellulases into a multienzyme complex through high-affinity type I cohesin–dockerin interactions, thereby enhancing synergistic cellulose and plant cell wall deconstruction. Its CBM3a targets the complex to cellulose, and its C-terminal X–DocII connects the complex to the cell via anchoring scaffoldins. (pinheiro2010novelinsightinto pages 47-50, xu2016dramaticperformanceof pages 1-2)
- Localization: CipA-enabled cellulosomes are predominantly cell surface-associated through anchoring scaffoldins bearing SLH domains. C. thermocellum also produces cell-free (diffusible) cellulosomes that operate at a distance from the bacterial surface, consistent with secondary scaffoldins lacking SLH modules. (pinheiro2009functionalinsightsinto pages 7-9, xu2016dramaticperformanceof pages 1-2)
- Pathway context: CipA is central to the exoproteome that deconstructs cellulose to cellodextrins for uptake and metabolism. Disruption of the primary scaffoldin alters expression of CAZymes and transport systems, underscoring its systems-level role in lignocellulose conversion. (xu2016dramaticperformanceof pages 1-2)
Recent developments and latest research (priority to 2023–2024)
- 2024 review on cellulose-binding domains for materials engineering: Detailed coverage of CBM-based functionalization strategies—including family 3 CBMs—demonstrates active 2024 work leveraging cellulosomal CBMs for material binding and enzyme immobilization. URL: https://doi.org/10.1186/s40643-024-00790-4 (Jul 2024). (li2024harnessingcellulosebindingprotein pages 10-10)
- 2023–2024 synthesis and engineering trends summarized in recent reviews: Emerging strategies to engineer cohesin–dockerin affinity and modularity and to apply CBMs/cohesins in designer assemblies are highlighted, informing CipA-like scaffoldin engineering and applications. While these summaries appear in a 2025 review, they draw on 2023–2024 primary sources on cohesin–dockerin tuning and CBM-enhanced activity/stability. (lindic2025structuralandfunctional pages 19-20, lindic2025structuralandfunctional pages 4-5)
- Genomic and ecological context (2024): Large-scale genomic analyses underscore the diversity and complexity of cellulosome-producing bacteria, with Acetivibrio/Clostridium thermocellum exemplifying complex cellulosomes and diverse enzyme complements, supporting CipA’s central role in such architectures. (lindic2025structuralandfunctional pages 19-20)
Current applications and real-world implementations
- Designer/synthetic cellulosomes: Modular scaffoldins and cohesin–dockerin pairs are widely used to build designer cellulosomes that recapitulate CipA-like architecture to enhance biomass deconstruction; design considerations include dockerin/cohesin selection, linker composition, and CBM choice. Results consistently show enhanced hydrolysis versus equivalent free-enzyme mixtures, though stability and context-dependence remain challenges in industrial settings. (lindic2025structuralandfunctional pages 4-5, li2024harnessingcellulosebindingprotein pages 10-10)
- Immobilization and materials functionalization: CBM-driven binding (including CBM3a derivatives) enables enzyme immobilization on cellulose and cellulose-like supports for biocatalysis and biosensing, aligning with CipA’s CBM3a targeting principle. 2024 examples include use of CBMs to functionalize cellulose materials and immobilize fusion proteins for improved performance. (li2024harnessingcellulosebindingprotein pages 10-10)
- Consolidated bioprocessing and heterologous expression: Prior implementations have expressed CipA variants and cellulosomal components in other clostridia to secrete self-assembling mini-cellulosomes, illustrating cross-species deployment of CipA-like scaffoldins and informing current CBP strategies. URL: https://doi.org/10.1186/1754-6834-6-117 (Aug 2013). ()
Expert opinions and authoritative analyses
- Mechanistic consensus: Primary scaffoldin CipA integrates enzymes via type I cohesins, targets cellulose via CBM3a, and anchors to the cell via type II interactions—yielding a highly synergistic macromolecular machine. Expert reviews emphasize the unmatched strength and specificity of cohesin–dockerin interactions and the functional necessity of Ca2+. (pinheiro2010novelinsightinto pages 47-50, santos2025unconventionalcohesindockerinbinding pages 46-49)
- Systems-level importance of CipA: Experimental deletions and exoproteome analyses support that CipA is the dominant determinant of high cellulose solubilization efficiency in C. thermocellum; intact CipA-mediated assembly affects gene regulation, transport, and particle-scale deconstruction mechanisms. URL: https://doi.org/10.1126/sciadv.1501254 (Feb 2016). (xu2016dramaticperformanceof pages 1-2)
Relevant quantitative statistics and data
- Domain and module counts: CipA carries nine type I cohesins and a single CBM3a, with a C-terminal X–DocII dyad. (pinheiro2010novelinsightinto pages 47-50, pinheiro2010novelinsightinto pages 37-40)
- System enzyme complement: The C. thermocellum genome encodes approximately 70+ dockerin-containing cellulosomal proteins in addition to free CAZymes, underscoring the potential multivalency of CipA-centered complexes. (pinheiro2009functionalinsightsinto pages 1-4)
- Binding properties: Cohesin–dockerin complexes are Ca2+-dependent, with dockerins containing duplicated EF-hand-like loops and capable of dual-binding orientations; the interaction is among the strongest non-covalent protein–protein interactions reported for modular assemblies. (santos2025unconventionalcohesindockerinbinding pages 46-49, pinheiro2010novelinsightinto pages 40-42)
Ambiguity check and domain alignment
- Ambiguity: The symbol “cipA” can be ambiguous across organisms; the organismal context here is explicitly C. thermocellum (A. thermocellus). All cited sources that name CipA refer to the C. thermocellum primary scaffoldin Cthe_3077, matching UniProt Q06851. (pinheiro2010novelinsightinto pages 47-50, pinheiro2009functionalinsightsinto pages 1-4)
- Domain/family alignment: Literature-confirmed domains (cohesins, CBM3a, X–DocII; anchoring via SLH-bearing secondary scaffoldins) align with UniProt/IPR annotations for cohesin domains (IPR002102) and CBM3-related domains (IPR001956; IPR036966). (pinheiro2010novelinsightinto pages 37-40, pinheiro2010novelinsightinto pages 47-50)
Data and source details with URLs and dates (where available)
- Xu et al., Science Advances, 2016—systems and genetic insights on CipA’s centrality and cell-free cellulosomes. URL: https://doi.org/10.1126/sciadv.1501254 (Feb 2016). (xu2016dramaticperformanceof pages 1-2)
- Li & Liu, Bioresources and Bioprocessing, 2024—2024 review on CBM-based material functionalization relevant to CBM3a uses in designer systems. URL: https://doi.org/10.1186/s40643-024-00790-4 (Jul 2024). (li2024harnessingcellulosebindingprotein pages 10-10)
- Pinheiro et al., Biochemical Journal, 2009—CipA architecture (nine type I cohesins, CBM3a, X–DocII) and cohesin/dockerin specificity mapping. URL: https://doi.org/10.1042/bj20091152 (Dec 2009). (pinheiro2009functionalinsightsinto pages 1-4)
- Pinheiro (2010) review—mechanistic overview of type I vs. type II cohesin–dockerin interactions; CipA’s 2 CohI–CBM3a–7 CohI–X–DocII map and anchoring partners with SLH modules. (pinheiro2010novelinsightinto pages 47-50, pinheiro2010novelinsightinto pages 37-40)
- Coh–Doc biophysics and dual-binding modes—general principles and strength/stoichiometry. (santos2025unconventionalcohesindockerinbinding pages 46-49, pinheiro2010novelinsightinto pages 40-42)
Conclusions
CipA (cipA; Cthe_3077; UniProt Q06851) is the primary scaffoldin of A. thermocellus/C. thermocellum cellulosomes. Its modular architecture—nine type I cohesins, a central CBM3a, and a C-terminal X–dockerin (type II)—orchestrates assembly of numerous dockerin-bearing CAZymes and anchors the complex to the cell surface through SLH-bearing secondary scaffoldins. CipA is essential for high-efficiency cellulose deconstruction, functioning at the interface of enzyme synergy, substrate targeting, and cell-surface attachment, with additional evidence for cell-free complexes in the exoproteome. Recent 2023–2024 advances emphasize modular engineering of CBMs/cohesins for designer cellulosomes and materials functionalization, reinforcing the translational value of the CipA paradigm. (pinheiro2010novelinsightinto pages 47-50, pinheiro2010novelinsightinto pages 37-40, xu2016dramaticperformanceof pages 1-2, li2024harnessingcellulosebindingprotein pages 10-10, santos2025unconventionalcohesindockerinbinding pages 46-49, pinheiro2009functionalinsightsinto pages 1-4)
References
(pinheiro2010novelinsightinto pages 47-50): BA Pinheiro. Novel insight into the mechanism of cellulosome assembly and plant cell wall hydrolysis in anaerobic bacteria. Unknown journal, 2010.
(pinheiro2009functionalinsightsinto pages 1-4): Benedita A. Pinheiro, Harry J. Gilbert, Kazutaka Sakka, Kazuo Sakka, Vânia O. Fernandes, José A. M. Prates, Victor D. Alves, David N. Bolam, Luís M. A. Ferreira, and Carlos M. G. A Fontes. Functional insights into the role of novel type i cohesin and dockerin domains from clostridium thermocellum. The Biochemical journal, 424 3:375-84, Dec 2009. URL: https://doi.org/10.1042/bj20091152, doi:10.1042/bj20091152. This article has 56 citations.
(pinheiro2010novelinsightinto pages 37-40): BA Pinheiro. Novel insight into the mechanism of cellulosome assembly and plant cell wall hydrolysis in anaerobic bacteria. Unknown journal, 2010.
(santos2025unconventionalcohesindockerinbinding pages 46-49): MRCD Santos. Unconventional cohesin-dockerin binding mechanisms reveal the complexity of cellulosome assembly. Unknown journal, 2025.
(pinheiro2010novelinsightinto pages 40-42): BA Pinheiro. Novel insight into the mechanism of cellulosome assembly and plant cell wall hydrolysis in anaerobic bacteria. Unknown journal, 2010.
(xu2016dramaticperformanceof pages 1-2): Qi Xu, Michael G. Resch, Kara Podkaminer, Shihui Yang, John O. Baker, Bryon S. Donohoe, Charlotte Wilson, Dawn M. Klingeman, Daniel G. Olson, Stephen R. Decker, Richard J. Giannone, Robert L. Hettich, Steven D. Brown, Lee R. Lynd, Edward A. Bayer, Michael E. Himmel, and Yannick J. Bomble. Dramatic performance of clostridium thermocellum explained by its wide range of cellulase modalities. Science Advances, Feb 2016. URL: https://doi.org/10.1126/sciadv.1501254, doi:10.1126/sciadv.1501254. This article has 166 citations and is from a highest quality peer-reviewed journal.
(pinheiro2009functionalinsightsinto pages 7-9): Benedita A. Pinheiro, Harry J. Gilbert, Kazutaka Sakka, Kazuo Sakka, Vânia O. Fernandes, José A. M. Prates, Victor D. Alves, David N. Bolam, Luís M. A. Ferreira, and Carlos M. G. A Fontes. Functional insights into the role of novel type i cohesin and dockerin domains from clostridium thermocellum. The Biochemical journal, 424 3:375-84, Dec 2009. URL: https://doi.org/10.1042/bj20091152, doi:10.1042/bj20091152. This article has 56 citations.
(li2024harnessingcellulosebindingprotein pages 10-10): Shaowei Li and Guodong Liu. Harnessing cellulose-binding protein domains for the development of functionalized cellulose materials. Bioresources and Bioprocessing, Jul 2024. URL: https://doi.org/10.1186/s40643-024-00790-4, doi:10.1186/s40643-024-00790-4. This article has 6 citations and is from a peer-reviewed journal.
(lindic2025structuralandfunctional pages 4-5): Nataša Lindič and Maša Vodovnik. Structural and functional insights into cellulosomes: masters of plant cell wall degradation. Frontiers in Microbiology, Sep 2025. URL: https://doi.org/10.3389/fmicb.2025.1638551, doi:10.3389/fmicb.2025.1638551. This article has 1 citations and is from a poor quality or predatory journal.
(lindic2025structuralandfunctional pages 19-20): Nataša Lindič and Maša Vodovnik. Structural and functional insights into cellulosomes: masters of plant cell wall degradation. Frontiers in Microbiology, Sep 2025. URL: https://doi.org/10.3389/fmicb.2025.1638551, doi:10.3389/fmicb.2025.1638551. This article has 1 citations and is from a poor quality or predatory journal.
---
id: Q06851
gene_symbol: cipA
aliases:
- CipA
- Cellulose-integrating protein A
- Cellulosomal glycoprotein S1/SL
- Cthe_3077
product_type: PROTEIN
status: DRAFT
taxon:
id: NCBITaxon:203119
label: Acetivibrio thermocellus (strain ATCC 27405 / DSM 1237 / JCM 9322 / NBRC
103400 / NCIMB 10682 / NRRL B-4536 / VPI 7372)
description: CipA is the primary cellulosomal scaffoldin protein in Acetivibrio thermocellus
(formerly Clostridium thermocellum). It is a large (1853 aa) non-catalytic structural
protein that serves as the central organizing scaffold of the cellulosome - a supramolecular
multi-enzyme complex that efficiently degrades plant cell wall polysaccharides.
CipA contains nine type I cohesin domains that bind dockerin-bearing catalytic enzymes
(cellulases, hemicellulases), a central CBM3a carbohydrate-binding module that targets
the complex to crystalline cellulose, and a C-terminal type II dockerin (with associated
X module) that anchors the cellulosome to cell-surface proteins bearing type II
cohesins (SdbA, OlpB, Orf2p). CipA does NOT possess any catalytic/enzymatic activity
- its function is purely structural and organizational, bringing multiple enzymes
into proximity for synergistic cellulose degradation.
existing_annotations:
- term:
id: GO:0000272
label: polysaccharide catabolic process
evidence_type: IEA
original_reference_id: GO_REF:0000120
review:
summary: CipA is involved in polysaccharide catabolism but only indirectly through
its scaffolding role. CipA itself has no catalytic activity; it organizes
dockerin-bearing enzymes that perform the actual hydrolysis. The annotation
captures participation in the process but overstates direct involvement.
action: KEEP_AS_NON_CORE
reason: While CipA is essential for efficient polysaccharide degradation by
the cellulosome, it is not directly involved in the catabolic process itself.
CipA is a non-catalytic structural organizer that assembles multiple cellulases
and hemicellulases into a multienzyme complex. The scaffoldin promotes enzyme
synergy but does not catalyze any reactions. This annotation is acceptable
as a secondary/non-core function reflecting its organizational role in the
process.
supported_by:
- reference_id: file:ACET2/cipA/cipA-deep-research-falcon.md
supporting_text: CipA is a non-catalytic structural organizer that assembles
multiple cellulases and hemicellulases into a multienzyme complex through
high-affinity type I cohesin-dockerin interactions
- term:
id: GO:0004553
label: hydrolase activity, hydrolyzing O-glycosyl compounds
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: This annotation is INCORRECT. CipA has no hydrolase activity whatsoever.
It is a non-catalytic scaffoldin protein that organizes enzymes but does not
itself possess any enzymatic function. This appears to be an erroneous transfer
from the dockerin domain (IPR002105), which is also present in catalytic cellulosomal
enzymes.
action: REMOVE
reason: CipA is explicitly described in the literature as a non-catalytic scaffolding
glycoprotein (UniProt CC-FUNCTION). The UniProt function annotation states
that CipA acts as a scaffolding protein in the cellulosome and promotes binding
of cellulose to the catalytic domains of the cellulolytic enzymes - note it
promotes binding TO catalytic domains, it does not have catalytic activity
itself. The deep research confirms CipA is a non-catalytic structural organizer
(cipA-deep-research-falcon.md). The InterPro domain IPR002105 (Dockerin_1_rpt)
is present in both scaffoldins and catalytic enzymes; the hydrolase activity
annotation was incorrectly transferred because dockerins are commonly found
in hydrolases, but the scaffoldin CipA only uses its dockerin (type II) for
anchoring to cell-surface proteins, not for catalysis. This is a clear over-annotation
error.
supported_by:
- reference_id: file:ACET2/cipA/cipA-deep-research-falcon.md
supporting_text: CipA is a non-catalytic structural organizer that assembles
multiple cellulases and hemicellulases into a multienzyme complex
- term:
id: GO:0005576
label: extracellular region
evidence_type: IEA
original_reference_id: GO_REF:0000044
review:
summary: This annotation is correct. CipA is a secreted protein that functions
in the extracellular space, either cell-surface anchored or as part of cell-free
cellulosomes.
action: ACCEPT
reason: UniProt explicitly states that CipA is secreted and remains at the cell
surface. The deep research confirms that CipA-enabled cellulosomes are predominantly
cell surface-associated through anchoring scaffoldins bearing SLH domains.
C. thermocellum also produces cell-free (diffusible) cellulosomes that operate
at a distance from the bacterial surface. The protein has a signal peptide
(residues 1-28) and functions extracellularly.
supported_by:
- reference_id: file:ACET2/cipA/cipA-deep-research-falcon.md
supporting_text: CipA-enabled cellulosomes are predominantly cell surface-associated
through anchoring scaffoldins bearing SLH domains. C. thermocellum also
produces cell-free (diffusible) cellulosomes that operate at a distance
from the bacterial surface
- term:
id: GO:0005975
label: carbohydrate metabolic process
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: This annotation is too general and misrepresents CipA's role. CipA
does not metabolize carbohydrates; it organizes enzymes that do. This is an
overly broad annotation derived from the CBM3 domain.
action: MODIFY
reason: CipA's CBM3a domain binds cellulose but does not metabolize it. The
protein's role is structural - organizing the cellulosome for efficient carbohydrate
degradation. A more appropriate annotation would be GO:0044575 (cellulosome
assembly) which captures the actual biological process CipA participates in.
The annotation to carbohydrate metabolic process incorrectly implies direct
metabolic activity.
proposed_replacement_terms:
- id: GO:0044575
label: cellulosome assembly
supported_by:
- reference_id: file:ACET2/cipA/cipA-deep-research-falcon.md
supporting_text: 'CBM3a function: targets crystalline cellulose to increase
local enzyme concentration and synergize hydrolysis; CBM3a is the prevalent
cellulosomal CBM in C. thermocellum'
- term:
id: GO:0030245
label: cellulose catabolic process
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: Similar to GO:0000272, this annotation captures CipA's indirect involvement
in cellulose degradation through its scaffolding function but overstates direct
participation in the catabolic process.
action: KEEP_AS_NON_CORE
reason: CipA is essential for efficient cellulose catabolism via the cellulosome,
but it does not itself degrade cellulose. Its CBM3a module targets the complex
to cellulose substrate, and its cohesins organize the catalytic enzymes that
perform hydrolysis. The annotation reflects involvement in the process but
should be considered non-core since CipA's primary function is structural
organization (cellulosome assembly) rather than direct catalysis.
supported_by:
- reference_id: file:ACET2/cipA/cipA-deep-research-falcon.md
supporting_text: CipA is essential for high-efficiency cellulose deconstruction,
functioning at the interface of enzyme synergy, substrate targeting, and
cell-surface attachment
- term:
id: GO:0030246
label: carbohydrate binding
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: This annotation is correct but could be made more specific. CipA binds
carbohydrates via its CBM3a domain, specifically binding crystalline cellulose.
action: ACCEPT
reason: 'CipA contains a well-characterized CBM3a (carbohydrate-binding module
family 3a) domain at positions 365-523. The deep research confirms that CBM3a
targets crystalline cellulose to increase local enzyme concentration and synergize
hydrolysis. CBM3a is the prevalent cellulosomal CBM in C. thermocellum (cipA-deep-research-falcon.md).
The crystal structure of this domain has been solved (PDB: 1NBC at 1.75 A
resolution). This is a core molecular function.'
supported_by:
- reference_id: file:ACET2/cipA/cipA-deep-research-falcon.md
supporting_text: 'CBM3a function: targets crystalline cellulose to increase
local enzyme concentration and synergize hydrolysis'
- term:
id: GO:0030248
label: cellulose binding
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: This annotation is correct and represents a core molecular function
of CipA. The CBM3a domain specifically binds crystalline cellulose.
action: ACCEPT
reason: "CipA's CBM3a domain (residues 365-523) specifically binds crystalline\
\ cellulose, targeting the cellulosome to its substrate. This is experimentally\
\ verified through structural studies - the crystal structure of the CBM3a\
\ domain was solved at 1.75 A resolution (PDB: 1NBC; Tormo et al., EMBO J\
\ 1996). The deep research states that CBM3a function targets crystalline\
\ cellulose to increase local enzyme concentration and synergize hydrolysis\
\ (cipA-deep-research-falcon.md). This is a core function of CipA - without\
\ cellulose binding, the cellulosome cannot target its substrate."
supported_by:
- reference_id: file:ACET2/cipA/cipA-deep-research-falcon.md
supporting_text: 'CBM3a function: targets crystalline cellulose to increase
local enzyme concentration and synergize hydrolysis'
- term:
id: GO:0071555
label: cell wall organization
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: This annotation is misleading. CipA is involved in PLANT cell wall
DEGRADATION (as a target substrate), not in bacterial cell wall organization.
The UniProt keyword mapping appears to have conflated cell wall degradation
with cell wall organization.
action: REMOVE
reason: CipA functions in the degradation of plant cell walls (cellulose, hemicellulose),
not in organizing the bacterial cell wall. While CipA is anchored at the cell
surface, its function is to organize the cellulosome for degrading extracellular
plant material, not to organize the bacterium's own cell wall. The UniProt
keywords include Cell wall biogenesis/degradation which likely triggered this
annotation, but the context is substrate degradation, not endogenous cell
wall organization. This is a semantic error in the automated annotation pipeline.
supported_by:
- reference_id: file:ACET2/cipA/cipA-deep-research-falcon.md
supporting_text: CipA's modular architecture orchestrates assembly of numerous
dockerin-bearing CAZymes and anchors the complex to the cell surface through
SLH-bearing secondary scaffoldins
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:14623971
review:
summary: This annotation is experimentally supported but should be made more
specific. PMID:14623971 reports the crystal structure of the cohesin-dockerin
complex, demonstrating that CipA's cohesin domains bind dockerin domains on
enzymes.
action: MODIFY
reason: 'The IPI annotation from PMID:14623971 is based on the crystal structure
of the type I cohesin-dockerin complex from C. thermocellum (WITH: UniProtKB:P51584,
XynY xylanase). The study demonstrates that the beta-sheet cohesin domain
interacts predominantly with one of the helices of the dockerin (PMID:14623971).
However, protein binding is too vague. CipA specifically binds type I dockerin
domains through its nine type I cohesin modules. The annotation should be
changed to GO:1990308 (type-I dockerin domain binding) which precisely describes
this molecular function.'
proposed_replacement_terms:
- id: GO:1990308
label: type-I dockerin domain binding
supported_by:
- reference_id: PMID:14623971
supporting_text: The data show that the beta-sheet cohesin domain interacts
predominantly with one of the helices of the dockerin.
additional_reference_ids: [PMID:14623971]
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:16384918
review:
summary: This annotation documents CipA's C-terminal type II dockerin binding
to type II cohesins on cell-surface anchoring proteins. The interaction demonstrated
is between CipA's X-DocII module and a type II cohesin from Cthe_1307.
action: MODIFY
reason: "PMID:16384918 reports the structure of the type II cohesin-dockerin\
\ complex involving CipA's C-terminal X-dockerin module (WITH: UniProtKB:A3DF10,\
\ Cthe_1307). The study describes an ultra-high-affinity complex between type\
\ II Doc together with its neighboring X module from the cellulosome scaffold\
\ of Clostridium thermocellum and a type II Coh module associated with the\
\ bacterial cell surface. The annotation should be more specific: GO:1990312\
\ (type-II cohesin domain binding) captures that CipA's dockerin binds to\
\ type II cohesins."
proposed_replacement_terms:
- id: GO:1990312
label: type-II cohesin domain binding
supported_by:
- reference_id: PMID:16384918
supporting_text: Here, we report the structure of an ultra-high-affinity
(K(a) = 1.44 x 10(10) M(-1)) complex between type II Doc, together with
its neighboring X module from the cellulosome scaffold of Clostridium
thermocellum, and a type II Coh module associated with the bacterial cell
surface.
additional_reference_ids: [PMID:16384918]
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:17360613
review:
summary: This annotation provides additional evidence for CipA's cohesin-dockerin
interactions, demonstrating a dual binding mode where dockerins can interact
with cohesins in two orientations.
action: MODIFY
reason: PMID:17360613 provides structural evidence for the dual binding mode
of type I dockerins to type I cohesins. The study shows that both repeats
could interact with cohesins by a common mechanism and that dockerins can
bind in a 180-degree rotated orientation (PMID:17360613). This further characterizes
the type I cohesin-dockerin interaction. As with PMID:14623971, the annotation
should be made more specific to GO:1990308 (type-I dockerin domain binding).
proposed_replacement_terms:
- id: GO:1990308
label: type-I dockerin domain binding
supported_by:
- reference_id: PMID:17360613
supporting_text: The dual binding mode is predicted to impart significant
plasticity into the orientation of the catalytic subunits within this
supramolecular assembly
additional_reference_ids: [PMID:17360613]
- term:
id: GO:0043263
label: cellulosome
evidence_type: IDA
original_reference_id: PMID:14623971
review:
summary: CipA is the primary structural component of the cellulosome. This cellular
component annotation is essential and missing from the current annotation
set.
action: NEW
reason: CipA is THE primary scaffoldin of the C. thermocellum cellulosome -
it IS the cellulosome scaffold. UniProt names it Cellulosomal-scaffolding
protein A and states it acts as a scaffolding protein in the cellulosome.
The deep research confirms that cipA encodes the primary cellulosomal scaffoldin
in Clostridium thermocellum (cipA-deep-research-falcon.md). This CC annotation
is critical for understanding CipA's identity and should be added with IDA
evidence based on direct characterization studies.
supported_by:
- reference_id: PMID:14623971
supporting_text: This megadalton catalytic machine organizes an enzymatic
consortium on a multifaceted molecular scaffold
additional_reference_ids: [cipA-deep-research-falcon.md]
- term:
id: GO:0044575
label: cellulosome assembly
evidence_type: IDA
original_reference_id: PMID:14623971
review:
summary: CipA's primary biological process is assembling the cellulosome by
recruiting dockerin-bearing enzymes. This is a core function that should be
annotated.
action: NEW
reason: CipA's nine type I cohesin domains bind dockerin-bearing enzymes, directly
assembling the cellulosome complex. PMID:14623971 reveals the structure of
the cohesin-dockerin complex from Clostridium thermocellum showing how cellulosome
assembly occurs. The deep research states that CipA is a non-catalytic structural
organizer that assembles multiple cellulases and hemicellulases into a multienzyme
complex through high-affinity type I cohesin-dockerin interactions (cipA-deep-research-falcon.md).
This is CipA's primary biological process.
supported_by:
- reference_id: PMID:14623971
supporting_text: This megadalton catalytic machine organizes an enzymatic
consortium on a multifaceted molecular scaffold whose "cohesin" domains
interact with corresponding "dockerin" domains of the enzymes.
additional_reference_ids: [cipA-deep-research-falcon.md]
- term:
id: GO:0005198
label: structural molecule activity
evidence_type: IDA
original_reference_id: PMID:14623971
review:
summary: CipA provides the structural framework of the cellulosome. This molecular
function annotation captures its non-catalytic scaffolding role.
action: NEW
reason: CipA contributes to the structural integrity of the cellulosome complex.
It is explicitly described as a non-catalytic scaffolding glycoprotein that
provides the structural backbone for enzyme assembly. Unlike catalytic cellulosomal
components, CipA's molecular function is purely structural - organizing and
maintaining the multi-enzyme complex. This annotation appropriately captures
that CipA's molecular function is structural organization rather than catalysis.
supported_by:
- reference_id: PMID:14623971
supporting_text: This megadalton catalytic machine organizes an enzymatic
consortium on a multifaceted molecular scaffold
additional_reference_ids: [cipA-deep-research-falcon.md]
core_functions:
- description: CipA's nine type I cohesin domains bind type I dockerin domains on
catalytic enzymes (cellulases, hemicellulases), recruiting them to the cellulosome
complex. This is the primary mechanism by which CipA organizes the multi-enzyme
complex.
molecular_function:
id: GO:1990308
label: type-I dockerin domain binding
directly_involved_in:
- id: GO:0044575
label: cellulosome assembly
locations:
- id: GO:0005576
label: extracellular region
supported_by:
- reference_id: PMID:14623971
supporting_text: The data show that the beta-sheet cohesin domain interacts
predominantly with one of the helices of the dockerin.
- reference_id: PMID:17360613
supporting_text: The dual binding mode is predicted to impart significant
plasticity into the orientation of the catalytic subunits within this supramolecular
assembly
- description: CipA's CBM3a domain (residues 365-523) specifically binds crystalline
cellulose, targeting the entire cellulosome complex to its substrate. This concentrates
the enzymatic machinery at the site of cellulose degradation.
molecular_function:
id: GO:0030248
label: cellulose binding
locations:
- id: GO:0005576
label: extracellular region
- description: CipA's C-terminal type II dockerin (with X module) binds type II
cohesins on cell-surface anchoring proteins (SdbA, OlpB, Orf2p), tethering the
cellulosome to the bacterial cell surface.
molecular_function:
id: GO:1990312
label: type-II cohesin domain binding
locations:
- id: GO:0005576
label: extracellular region
supported_by:
- reference_id: PMID:16384918
supporting_text: Here, we report the structure of an ultra-high-affinity (K(a)
= 1.44 x 10(10) M(-1)) complex between type II Doc, together with its neighboring
X module from the cellulosome scaffold of Clostridium thermocellum, and
a type II Coh module associated with the bacterial cell surface.
- description: CipA provides structural molecule activity as the primary scaffoldin
that assembles the cellulosome by integrating dockerin-bearing enzymes, binding
substrate via CBM3a, and anchoring to the cell surface.
molecular_function:
id: GO:0005198
label: structural molecule activity
directly_involved_in:
- id: GO:0044575
label: cellulosome assembly
locations:
- id: GO:0005576
label: extracellular region
references:
- id: GO_REF:0000002
title: Gene Ontology annotation through association of InterPro records with GO
terms
findings: []
- id: GO_REF:0000043
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
findings: []
- id: GO_REF:0000044
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location
vocabulary mapping
findings: []
- id: GO_REF:0000120
title: Combined Automated Annotation using Multiple IEA Methods
findings: []
- id: PMID:14623971
title: Cellulosome assembly revealed by the crystal structure of the cohesin-dockerin
complex
findings:
- statement: First crystal structure of type I cohesin-dockerin complex at 2.2
A resolution
supporting_text: Here we report the structure of the cohesin-dockerin complex
from Clostridium thermocellum at 2.2-A resolution.
- statement: Demonstrates structural basis for cellulosome assembly via cohesin-dockerin
interaction
supporting_text: This megadalton catalytic machine organizes an enzymatic
consortium on a multifaceted molecular scaffold whose "cohesin" domains
interact with corresponding "dockerin" domains of the enzymes.
- statement: Shows dockerin internal symmetry suggesting dual binding mode
supporting_text: Significantly, internal sequence duplication within the dockerin
is manifested in near-perfect internal twofold symmetry, suggesting that
both "halves" of the dockerin may interact with cohesins in a similar manner
- id: PMID:16384918
title: Mechanism of bacterial cell-surface attachment revealed by the structure
of cellulosomal type II cohesin-dockerin complex
findings:
- statement: Crystal structure of type II cohesin-dockerin complex with ultra-high
affinity
supporting_text: Here, we report the structure of an ultra-high-affinity (K(a)
= 1.44 x 10(10) M(-1)) complex between type II Doc, together with its neighboring
X module from the cellulosome scaffold of Clostridium thermocellum, and
a type II Coh module associated with the bacterial cell surface.
- statement: X module enhances dockerin stability and cohesin recognition
supporting_text: Identification of X module-Doc and X module-Coh contacts
reveal roles for the X module in Doc stability and enhanced Coh recognition.
- id: PMID:17360613
title: Evidence for a dual binding mode of dockerin modules to cohesins
findings:
- statement: Demonstrates dual binding mode imparts plasticity to cellulosome
structure
supporting_text: The dual binding mode is predicted to impart significant
plasticity into the orientation of the catalytic subunits within this supramolecular
assembly
- id: cipA-deep-research-falcon.md
title: Deep research summary of CipA function
findings:
- statement: Comprehensive literature synthesis confirms CipA is a non-catalytic
scaffoldin
supporting_text: CipA is a non-catalytic structural organizer that assembles
multiple cellulases and hemicellulases into a multienzyme complex through
high-affinity type I cohesin-dockerin interactions
proposed_new_terms: []
suggested_questions:
- question: Are there conditions under which CipA might directly participate in
carbohydrate modification or processing beyond its scaffolding role?
experts: []
suggested_experiments:
- description: Comprehensive interactome analysis of CipA cohesin domains to quantify
the full repertoire of dockerin-bearing proteins recruited to the cellulosome
in vivo.
hypothesis: While the cohesin-dockerin interaction is well-characterized structurally,
the complete set of CipA interaction partners in vivo remains incompletely defined.
tags: [cellulosome]