Alginate O-acetylation

Comparative transmembrane acylation review defines the proposed relay and its unresolved steps.

PMID:40821665

Comparative Azotobacter review provides nomenclature and physiological scope, with mechanistic generalizations checked against primary studies.

Direct interaction and structural work identifies a noncatalytic role for AlgF.

Direct AlgJ/AlgX biochemistry separates esterase assays from polymer transfer.

Native Azotobacter algF mutation establishes an acetylation role outside Pseudomonas.

The review integrates direct target biochemistry, native genetics and explicit homology inference. Scope is ABSTRACT and generalized to the Pseudomonas and Azotobacter lineages that carry the algIJFX (algIVFX) genes, with P. aeruginosa as the experimental reference, P. putida KT2440 as the second Pseudomonas exemplar and A. vinelandii as the cross-genus exemplar supported by a native algF mutant; no further organisms are added without target evidence. All four roles have family descriptors and verified exemplars. InterPro AlgI/AlgF family entries and AlgJ/AlgX domain entries are the descriptor term ids (every representative carries them); their labels are the InterPro short names quoted from the representatives' UniProt DR lines, since InterPro is not label-validated by the ontology adapters. AlgI is the only member with a PANTHER family, PTHR13285 (official label ACYLTRANSFERASE), reviewed in interpro/panther/PTHR13285/PTHR13285-review.yaml; it is too broad to be the AlgI family term, and its SF23 subfamily (TEICHOIC ACID D-ALANYLTRANSFERASE) mixes DltB, PatA and AlgI, so neither is asserted and its label is not evidence of AlgI substrate specificity. The family-root PAINT node supports only the broad acyltransferase activity asserted here. AlgF is not assigned intrinsic acetyltransferase activity solely because it is required for acetylation. GO:0051979 is not a descendant of GO:0042121; modification and polymer biosynthesis/export are distinct roles. The lack of a substrate-specific AlgX GO term is an ontology note, not an unknown biological mechanism. New provider requests failed; manually inspected primary literature and genuine existing reports are documented in the notes.

5Nodes

4Parts

0Variant Sets

0Variants

4Annotons

4Connections

Derived QC

Recommended-field compliance

100.0% recommended fields populated

All recommended fields populated.

Module deep research

✗ none found

No MODULE:alginate_o_acetylation deep-research report alongside the module YAML.

Leaf nodes lacking representative members

✓ representative grounding skipped for abstract module.

Template conformance

✓ every declared conforms_to bundle matches its template motif.

Function consistency and core coverage

6 gene-function check(s) reflected in core functions · 0 conflict(s) · 2 evidence or coverage gap(s) (8 comparison(s))

Retained noncore functions are reported separately; they do not require promotion to core functions. Support from representative genes does not establish conservation across the whole family. Missing reviews or identifiers leave a claim unverified.

Annoton	Participant	Function	Assessment
algI_acyltransferase_activity	algI (Pseudomonas putida KT2440) UniProtKB:Q88ND2 Family Representative	acyltransferase activity GO:0016746	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
algI_acyltransferase_activity	algI (Pseudomonas aeruginosa) UniProtKB:Q51392 Family Representative	acyltransferase activity GO:0016746	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
algI_acyltransferase_activity	algI (Azotobacter vinelandii ATCC 9046) UniProtKB:O52196 Family Representative	acyltransferase activity GO:0016746	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
algX_o_acetyltransferase_activity	algX (Pseudomonas putida KT2440) UniProtKB:Q88ND0 Family Representative	O-acetyltransferase activity GO:0016413	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
algX_o_acetyltransferase_activity	algX (Pseudomonas aeruginosa) UniProtKB:Q51372 Family Representative	O-acetyltransferase activity GO:0016413	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
algX_o_acetyltransferase_activity	algX (Azotobacter vinelandii ATCC 9046) UniProtKB:O52194 Family Representative	O-acetyltransferase activity GO:0016413	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
algI_acyltransferase_activity	AlgI family InterPro:IPR028362 Family	acyltransferase activity GO:0016746	Family Review Missing No supported structured family review is available for InterPro:IPR028362.
algX_o_acetyltransferase_activity	AlgX polymer-modification and export-associated family Family	O-acetyltransferase activity GO:0016413	Family Id Missing The family has no identifier linking it to a curated family review.

Gene-review completeness (12/12 grounded genes reviewed)

12 complete review(s) · 1 with deep research · 0 missing review · 11 reviewed but lacking deep research

Gene	Review	Complete	Deep research
algF P70799	✓	✓	✗
algF Q06062	✓	✓	✗
algF Q88ND4	✓	✓	✓
algI O52196	✓	✓	✗
algI Q51392	✓	✓	✗
algI Q88ND2	✓	✓	✗
algJ Q51393	✓	✓	✗
algJ Q88ND3	✓	✓	✗
algV O52197	✓	✓	✗
algX O52194	✓	✓	✗
algX Q51372	✓	✓	✗
algX Q88ND0	✓	✓	✗

Tree

Alginate O-acetylationBiological Processalginate_o_acetylation

Parts
1. 1. inner-membrane acetyl-donor transfer
2. AlgI membrane acetyl-transfer componentReactionalgI_membrane_transfer
  
  Annotons
  - AlgI membrane acyltransferase Family: AlgI family
3. 2. periplasm-facing acetyl relay
4. AlgJ/AlgV SGNH relay componentReactionalgJ_relay
  
  Annotons
  - AlgJ/AlgV periplasm-facing acetylation component Family: AlgJ/AlgV SGNH acetylation-component family
5. 3. periplasmic accessory support
6. AlgF periplasmic accessory componentBiological ProcessalgF_accessory
  
  Annotons
  - AlgF accessory protein Family: AlgF family
7. 4. terminal polymer O-acetylation
8. AlgX alginate O-acetyltransferaseReactionalgX_polymer_transfer
  
  Annotons
  - AlgX terminal O-acetyltransferase Family: AlgX polymer-modification and export-associated family

Details

Context

Pseudomonas and Azotobacter alginate-acetylating lineagesNCBITaxon:135621

Review places alginate acetylation in selected Pseudomonas and Azotobacter lineages and distinguishes the proposed MBOAT/SGNH relay from experiments on other polymers.

PMID:40821665

Comparative Azotobacter review identifies the AlgI/AlgV/AlgF/AlgX implementation; its categorical donor and enzyme descriptions are qualified by primary evidence.

A native Azotobacter nonpolar algF mutant produces unacetylated alginate, supporting cross-genus process conservation.

Brown-algal alginate production and other bacterial surface-polymer acylation systems do not establish this module. Current selected native proteins span P. aeruginosa PAO1-derived experiments, P. putida KT2440 and A. vinelandii ATCC 9046.

Alginate O-acetylationBiological Processalginate_o_acetylation

Four complementary roles in alginate acetylation; part ordering is presentational and does not establish a linear sequence of four catalytic reactions.

alginic acid acetylationGO:0051979

Context

Pseudomonas and Azotobacter alginate-acetylating lineagesNCBITaxon:135621

Review places alginate acetylation in selected Pseudomonas and Azotobacter lineages and distinguishes the proposed MBOAT/SGNH relay from experiments on other polymers.

PMID:40821665

Comparative Azotobacter review identifies the AlgI/AlgV/AlgF/AlgX implementation; its categorical donor and enzyme descriptions are qualified by primary evidence.

A native Azotobacter nonpolar algF mutant produces unacetylated alginate, supporting cross-genus process conservation.

Connections

algI_membrane_transfer -> algJ_relay Provides Input For

Proposed acetyl delivery from AlgI to the periplasmic AlgJ/AlgV component; native association is demonstrated for Pa, but the chemical intermediate is not.

Pa AlgI and AlgJ associate in native co-immunoprecipitation experiments.

The full AlgI-to-AlgJ acyl-shuttle model remains experimentally incomplete.

algJ_relay -> algX_polymer_transfer Provides Input For

Proposed acetyl handoff to AlgX; the physiological AlgJ donor/acceptor pair and direct transfer remain unresolved.

AlgJ and AlgX have distinct biochemical roles; only AlgX directly modifies the tested polymer.

The review identifies AlgJ-to-AlgX handoff as the major unresolved mechanistic step.

algF_accessory -> algJ_relay Provides Input For

Provides interaction/assembly context, not an asserted acetyl substrate. Pairwise binding supports this model; simultaneous bridging is not established.

Direct KT2440 pairwise AlgF interactions and Pa AlgF-AlgX association support organization of the acetylation machinery.

algF_accessory -> algX_polymer_transfer Provides Input For

Provides interaction/assembly context, not an asserted acetyl substrate. Pairwise binding supports this model; simultaneous bridging is not established.

Direct KT2440 pairwise AlgF interactions and Pa AlgF-AlgX association support organization of the acetylation machinery.

Part 1: inner-membrane acetyl-donor transfer

AlgI membrane acetyl-transfer componentReactionalgI_membrane_transfer

Annotons

AlgI membrane acyltransferase

algI_acyltransferase_activity

Participant: Family: AlgI family

Family:

AlgI familyInterPro:IPR028362

Representative Members: algI (Pseudomonas putida KT2440)UniProtKB:Q88ND2 algI (Pseudomonas aeruginosa)UniProtKB:Q51392 algI (Azotobacter vinelandii ATCC 9046)UniProtKB:O52196

Required Function:

acyltransferase activityGO:0016746

Function

acyltransferase activityGO:0016746

Processes

alginic acid acetylationGO:0051979

Locations

plasma membraneGO:0005886

Multipass membrane component required for acetylation. MBOAT ancestry supports an acyltransferase role, but neither the immediate physiological donor nor the complete target-specific covalent relay has been experimentally reconstructed. The proposed C-terminal acyl-shuttle mechanism is informed by Dlt and PatA systems rather than demonstrated AlgI chemistry.

PMID:12003941

Nonpolar mutants lose alginate O-acetylation; topology places AlgI across the inner membrane.

PMID:31900562

Mutant complementation and stability studies connect AlgI to the acetylation complex; the accessible record supports this at abstract level.

Native P. aeruginosa co-immunoprecipitation supports AlgI association with AlgJ.

Review explicitly qualifies the complete proposed alginate acyl-shuttle model.

Part 2: periplasm-facing acetyl relay

AlgJ/AlgV SGNH relay componentReactionalgJ_relay

Annotons

AlgJ/AlgV periplasm-facing acetylation component

algJ_relay_role

Participant: Family: AlgJ/AlgV SGNH acetylation-component family

Family:

AlgJ/AlgV SGNH acetylation-component family The ortholog group is represented by verified proteins. The specific InterPro domain is recorded separately as required_domain, rather than mislabeled as a full-length family identifier. In Azotobacter the acetylation homolog is called AlgV; a separate historical AlgJ designation names the export protein and is excluded.

Representative Members: algJ (Pseudomonas putida KT2440)UniProtKB:Q88ND3 algJ (Pseudomonas aeruginosa)UniProtKB:Q51393 algV (Azotobacter vinelandii ATCC 9046)UniProtKB:O52197

Required Domain:

Alginate O-acetyltranferase AlgJInterPro:IPR034657

Processes

alginic acid acetylationGO:0051979

Locations

plasma membraneGO:0005886 periplasmic spaceGO:0042597

Membrane-associated periplasmic SGNH protein required for alginate acetylation. P. putida and P. aeruginosa AlgJ have directly measured acetylesterase activity with artificial substrates; the physiological relay substrate and transfer to AlgX remain unresolved. The module therefore records the proposed contribution without equating in-vitro hydrolysis with the native reaction.

Both Pseudomonas AlgJ proteins have measured acetylesterase activity. Pa AlgJ has weak or undetectable polymer binding; direct polymer acetyl transfer was demonstrated for AlgX and was not established for AlgJ.

AlgJ exhibits acetylesterase activity in vitro.

KT2440 AlgF-AlgJ binding is directly measured by ITC; Pa native AlgI-AlgJ association supports complex organization.

Azotobacter algV is sequenced in the native alginate locus; this is not a purified AlgV assay.

Part 3: periplasmic accessory support

AlgF periplasmic accessory componentBiological ProcessalgF_accessory

Annotons

AlgF accessory protein

algF_accessory_role

Participant: Family: AlgF family

Family:

AlgF familyInterPro:IPR035422

Representative Members: algF (Pseudomonas putida KT2440)UniProtKB:Q88ND4 algF (Pseudomonas aeruginosa)UniProtKB:Q06062 algF (Azotobacter vinelandii ATCC 9046)UniProtKB:P70799

Processes

alginic acid acetylationGO:0051979

Locations

periplasmic spaceGO:0042597

Periplasmic noncatalytic component. KT2440 AlgF binds AlgJ and AlgX in separate in-vitro assays and lacks detected acetylesterase activity; P. aeruginosa AlgF has native AlgX association and no detected isolated polymannuronate binding. These support an interaction-mediator model, but simultaneous ternary bridging and exact acetyl-relay geometry remain proposed. Native Azotobacter algF genetics supports participation without establishing its molecular interaction mechanism.

Target-specific structural, binding and association studies support an interaction role, with the Pseudomonas species and constructs distinguished.

PMID:31900562

AlgF deletion affects acetylation and production/stability in the studied P. aeruginosa background.

The Azotobacter nonpolar algF mutant produces unacetylated alginate.

As expected, AJ34 produced unacetylated alginate.

Part 4: terminal polymer O-acetylation

AlgX alginate O-acetyltransferaseReactionalgX_polymer_transfer

Annotons

AlgX terminal O-acetyltransferase

algX_o_acetyltransferase_activity

Participant: Family: AlgX polymer-modification and export-associated family

Family:

AlgX polymer-modification and export-associated family The ortholog group is represented by verified proteins. The specific InterPro domain is recorded separately as required_domain, rather than mislabeled as a full-length family identifier. Characterized full-length members also contain an AlgX C-terminal carbohydrate-binding module (InterPro:IPR031798); the N-terminal signature alone does not prove polymer binding or the full activity.

Representative Members: algX (Pseudomonas putida KT2440)UniProtKB:Q88ND0 algX (Pseudomonas aeruginosa)UniProtKB:Q51372 algX (Azotobacter vinelandii ATCC 9046)UniProtKB:O52194

Required Function:

O-acetyltransferase activityGO:0016413

Required Domain:

Alginate biosynthesis protein AlgX, N-terminalInterPro:IPR034655

Function

O-acetyltransferase activityGO:0016413

Substrates: unacetylated mannuronate residues in alginate

Products: O-acetylated mannuronate residues in alginate

Processes

alginic acid acetylationGO:0051979

Locations

periplasmic spaceGO:0042597

Terminal polymer-modifying enzyme. P. aeruginosa AlgX directly transfers acetyl groups from an artificial donor to polymannuronate; its catalytic-site mutants secrete nonacetylated polymer. KT2440 AlgX has directly measured acetylesterase activity, polymer binding and an AlgK-complex structure; polymer acetyl transfer is inferred from the characterized homolog. P. putida binding lacks the increasing-affinity length trend reported for P. aeruginosa. Azotobacter chemistry remains homolog-based. Native AlgX also contributes to polymer protection/export, but this module represents its modification role.

P. aeruginosa AlgX directly O-acetylates polymannuronate using a surrogate donor.

PMID:23779107

Catalytic-site mutations abolish alginate acetylation in vivo; accessible primary abstract supports the mutation conclusion.

PMID:36494359

KT2440 AlgKX structure and polymer-binding experiments establish target-specific architecture and affinity behavior; Pa native interface disruption affects secretion/biofilm attachment.