SHY1

UniProt ID: P53266
Organism: Saccharomyces cerevisiae
Review Status: COMPLETE
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Gene Description

SHY1 encodes the yeast SURF1-family cytochrome c oxidase assembly factor. Shy1 is an intrinsic mitochondrial inner membrane protein required for efficient complex IV biogenesis, acting during early Cox1 maturation and coupling Cox1 translational regulation by the Mss51/Cox14 module to downstream complex IV assembly. Shy1 is not a mature cytochrome c oxidase subunit and is not a general unfolded-protein chaperone; its core role is assembly of mitochondrial respiratory chain complex IV.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0033617 mitochondrial respiratory chain complex IV assembly
IBA
GO_REF:0000033
ACCEPT
Summary: The PANTHER/IBA annotation is consistent with direct yeast evidence and conserved SURF1-family biology. Shy1 is repeatedly shown to be required for efficient cytochrome c oxidase assembly and Cox1 maturation.
Reason: Core biological process for SHY1.
Supporting Evidence:
PMID:17882259
Shy1 is an assembly factor for complex IV in Saccharomyces cerevisiae
file:yeast/SHY1/SHY1-deep-research-falcon.md
Falcon deep research identifies SHY1 as a SURF1-family mitochondrial inner membrane complex IV assembly factor.
GO:0005739 mitochondrion
IBA
GO_REF:0000033
ACCEPT
Summary: Mitochondrial localization is correct for Shy1. The more specific mitochondrial inner membrane term is also present, but the broader mitochondrion annotation is supported by direct studies and family transfer.
Reason: Shy1 performs its assembly-factor function in mitochondria.
Supporting Evidence:
PMID:9162072
An antibody against the carboxyl-terminal half of Shy1p has been used to localize the protein in the inner mitochondrial membrane.
GO:0005743 mitochondrial inner membrane
IEA
GO_REF:0000044
ACCEPT
Summary: UniProt subcellular-location mapping to mitochondrial inner membrane is accurate and agrees with direct localization experiments.
Reason: Core localization for Shy1.
Supporting Evidence:
PMID:9162072
An antibody against the carboxyl-terminal half of Shy1p has been used to localize the protein in the inner mitochondrial membrane.
GO:0016020 membrane
IEA
GO_REF:0000002
MODIFY
Summary: InterPro transfer to the generic membrane term is directionally correct for a SURF1-family membrane protein but too broad for this curated review. Shy1 is specifically an inner mitochondrial membrane protein.
Reason: Replace generic membrane with the experimentally supported mitochondrial inner membrane location.
Proposed replacements: mitochondrial inner membrane
Supporting Evidence:
PMID:9162072
An antibody against the carboxyl-terminal half of Shy1p has been used to localize the protein in the inner mitochondrial membrane.
GO:0005515 protein binding
IPI
PMID:17882259
Shy1 couples Cox1 translational regulation to cytochrome c o...
MARK AS OVER ANNOTATED
Summary: Shy1 interactions with Cox14, Mss51, Coa1 and complex IV assembly intermediates are central to its biology, but the generic protein binding term is not informative. The functional consequence is complex IV assembly rather than protein binding as a standalone molecular function.
Reason: Use complex IV assembly and mitochondrial inner membrane annotations instead of generic protein binding.
Supporting Evidence:
PMID:17882259
Shy1 interacts with Mss51 and Cox14, translational regulators of Cox1.
GO:0005515 protein binding
IPI
PMID:17882260
Coa1 links the Mss51 post-translational function to Cox1 cof...
MARK AS OVER ANNOTATED
Summary: The Coa1/Shy1 interaction supports the assembly pathway model but does not justify retaining a generic protein binding MF annotation.
Reason: The interaction is better represented as part of complex IV assembly.
Supporting Evidence:
PMID:17882260
The interaction between Coa1 and Cox1, and the physical and genetic interactions between Coa1 and Mss51, Shy1 and Cox14 suggest that Coa1 coordinates the transition
GO:0016020 membrane
IDA
PMID:15306853
Mss51p and Cox14p jointly regulate mitochondrial Cox1p expre...
MODIFY
Summary: The direct membrane annotation is valid but less specific than the mitochondrial inner membrane annotations supported by SHY1 localization and function.
Reason: Use the specific inner mitochondrial membrane component term.
Proposed replacements: mitochondrial inner membrane
Supporting Evidence:
PMID:9162072
An antibody against the carboxyl-terminal half of Shy1p has been used to localize the protein in the inner mitochondrial membrane.
GO:0005777 peroxisome
HDA
PMID:35563734
Pls1 Is a Peroxisomal Matrix Protein with a Role in Regulati...
KEEP AS NON CORE
Summary: Retain as non-core only. The canonical and mechanistic Shy1 localization is the mitochondrial inner membrane. The peroxisome annotation comes from a high-throughput peroxisomal screen and has no demonstrated role in Shy1's complex IV assembly function.
Reason: Possible context-specific or high-throughput localization, not the core functional location.
Supporting Evidence:
PMID:35563734
we used a high-throughput screen to discover peroxisomal proteins in yeast.
GO:0005739 mitochondrion
HDA
PMID:24769239
Quantitative variations of the mitochondrial proteome and ph...
ACCEPT
Summary: High-throughput mitochondrial proteomics detection is consistent with Shy1's established mitochondrial role.
Reason: Correct broad mitochondrial localization.
Supporting Evidence:
PMID:24769239
we performed an overall quantitative proteomic and phosphoproteomic study of isolated mitochondria extracted from yeast grown on fermentative (glucose or galactose) and respiratory (lactate) media
GO:0005739 mitochondrion
HDA
PMID:16823961
Toward the complete yeast mitochondrial proteome: multidimen...
ACCEPT
Summary: Mitochondrial proteome detection is consistent with Shy1's canonical localization and function.
Reason: Correct broad mitochondrial localization.
Supporting Evidence:
PMID:16823961
A total of 851 different proteins (PROMITO dataset) were identified by use of multidimensional LC-MS/MS, 1D-SDS-PAGE combined with nano-LC-MS/MS and 2D-PAGE
GO:0005743 mitochondrial inner membrane
IDA
PMID:15306853
Mss51p and Cox14p jointly regulate mitochondrial Cox1p expre...
ACCEPT
Summary: Inner mitochondrial membrane localization is appropriate for Shy1's role in Cox1 maturation and complex IV assembly.
Reason: Core cellular component for Shy1 function.
Supporting Evidence:
PMID:15306853
The release of Mss51p from the complex occurs at a downstream step in the assembly pathway, probably catalyzed by Shy1p.
GO:0005743 mitochondrial inner membrane
IDA
PMID:9162072
SHY1, the yeast homolog of the mammalian SURF-1 gene, encode...
ACCEPT
Summary: The original SHY1 characterization directly localized Shy1 to the inner mitochondrial membrane.
Reason: Direct localization evidence for the core site of action.
Supporting Evidence:
PMID:9162072
An antibody against the carboxyl-terminal half of Shy1p has been used to localize the protein in the inner mitochondrial membrane.
GO:0033617 mitochondrial respiratory chain complex IV assembly
IMP
PMID:17882259
Shy1 couples Cox1 translational regulation to cytochrome c o...
ACCEPT
Summary: Strong mutant and biochemical evidence supports Shy1 as a complex IV assembly factor that links Cox1 translational control with assembly intermediate progression.
Reason: Core biological process supported by direct experimental evidence.
Supporting Evidence:
PMID:17882259
We suggest that Shy1 links Cox1 translational regulation to complex IV assembly and supercomplex formation.
GO:0051082 unfolded protein binding
IMP
PMID:11389896
Shy1p occurs in a high molecular weight complex and is requi...
MARK AS OVER ANNOTATED
Summary: The evidence shows that Shy1 occurs in an assembly-associated complex and is required for efficient cytochrome c oxidase assembly. It does not show general unfolded-protein binding or a broad chaperone substrate range.
Reason: The annotation over-interprets an assembly-factor phenotype. Shy1 should be curated to complex IV assembly rather than generic unfolded protein binding.
Supporting Evidence:
PMID:11389896
Shy1p may either facilitate assembly of the enzyme, or increase its stability.
GO:0005743 mitochondrial inner membrane
IDA
PMID:9162072
SHY1, the yeast homolog of the mammalian SURF-1 gene, encode...
ACCEPT
Summary: Duplicate direct UniProt annotation for Shy1 inner mitochondrial membrane localization; retain because it accurately reflects the original experimental localization.
Reason: Direct localization evidence for the core site of action.
Supporting Evidence:
PMID:9162072
An antibody against the carboxyl-terminal half of Shy1p has been used to localize the protein in the inner mitochondrial membrane.

Core Functions

Shy1 is a SURF1-family mitochondrial inner membrane assembly factor for cytochrome c oxidase. It acts during Cox1 maturation and assembly intermediate progression, linking Mss51/Cox14-dependent Cox1 translational regulation to complex IV assembly and supercomplex formation.

Supporting Evidence:
  • PMID:17882259
    We suggest that Shy1 links Cox1 translational regulation to complex IV assembly and supercomplex formation.
  • file:yeast/SHY1/SHY1-deep-research-falcon.md
    Falcon deep research emphasizes Cox1 maturation and complex IV assembly as the core SHY1 function.

References

Gene Ontology annotation through association of InterPro records with GO terms
Annotation inferences using phylogenetic trees
Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt
Shy1p occurs in a high molecular weight complex and is required for efficient assembly of cytochrome c oxidase in yeast.
  • Shy1 is required for efficient complex IV assembly but residual normal enzyme can still form.
    "Steady-state levels of the enzyme were found to be strongly reduced, the total amount of assembled complex being approximately 30% of control."
Mss51p and Cox14p jointly regulate mitochondrial Cox1p expression in Saccharomyces cerevisiae.
  • Shy1 likely acts downstream of the Cox14-Cox1-Mss51 regulatory complex.
    "The release of Mss51p from the complex occurs at a downstream step in the assembly pathway, probably catalyzed by Shy1p."
Toward the complete yeast mitochondrial proteome: multidimensional separation techniques for mitochondrial proteomics.
Shy1 couples Cox1 translational regulation to cytochrome c oxidase assembly.
  • Shy1 is a complex IV assembly factor that interacts with Cox1 translational regulators and assembly intermediates.
    "Shy1 interacts with Mss51 and Cox14, translational regulators of Cox1."
Coa1 links the Mss51 post-translational function to Cox1 cofactor insertion in cytochrome c oxidase assembly.
  • Coa1 and Shy1 participate in the Cox1 maturation/cofactor insertion step of complex IV assembly.
    "Shy1 has been implicated in formation of the heme a3-Cu(B) site in Cox1."
Quantitative variations of the mitochondrial proteome and phosphoproteome during fermentative and respiratory growth in Saccharomyces cerevisiae.
Pls1 Is a Peroxisomal Matrix Protein with a Role in Regulating Lysine Biosynthesis.
SHY1, the yeast homolog of the mammalian SURF-1 gene, encodes a mitochondrial protein required for respiration.
  • SHY1 encodes the yeast SURF1 homolog and localizes to the inner mitochondrial membrane.
    "The encoded protein is homologous to the product of the mammalian SURF-1 gene."
file:yeast/SHY1/SHY1-deep-research-falcon.md
Falcon deep research report on SHY1
  • Falcon synthesis identifies SHY1 as a SURF1-family inner mitochondrial membrane complex IV assembly factor.

Suggested Questions for Experts

Q: Is there enough direct evidence to annotate a specific Shy1 molecular function for Cox1 cofactor insertion or assembly-intermediate stabilization, rather than leaving SHY1 represented only by the biological-process term for complex IV assembly?

Suggested experts: Mick DU, Rehling P, Winge DR

Suggested Experiments

Experiment: Reconstitute Shy1-containing Cox1 assembly intermediates with Cox14, Mss51, Coa1 and cofactor-insertion factors, then test Shy1 mutants for Cox1 cofactor incorporation, assembly-intermediate stability, and release of Mss51.

Hypothesis: Shy1 promotes Cox1 heme a3:CuB maturation or maintains Cox1 in an assembly-competent state rather than binding unfolded proteins generally.

Type: mitochondrial complex IV assembly intermediate assay

📚 Additional Documentation

Deep Research Falcon

(SHY1-deep-research-falcon.md)

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gene_info: Name=SHY1; OrderedLocusNames=YGR112W; ORFNames=G6150;
organism_full: Saccharomyces cerevisiae (strain ATCC 204508 / S288c) (Baker's yeast).
protein_family: Belongs to the SURF1 family. .
protein_domains: Surf1/Shy1. (IPR002994); Surf1/Surf4. (IPR045214); SURF1 (PF02104)
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Question

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

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.

Target Gene/Protein Identity (from UniProt):

  • UniProt Accession: P53266
  • Protein Description: RecName: Full=Cytochrome oxidase assembly protein SHY1; AltName: Full=SURF1 homolog of Yeast; AltName: Full=SURF1-like protein;
  • Gene Information: Name=SHY1; OrderedLocusNames=YGR112W; ORFNames=G6150;
  • Organism (full): Saccharomyces cerevisiae (strain ATCC 204508 / S288c) (Baker's yeast).
  • Protein Family: Belongs to the SURF1 family. .
  • Key Domains: Surf1/Shy1. (IPR002994); Surf1/Surf4. (IPR045214); SURF1 (PF02104)

MANDATORY VERIFICATION STEPS:

  1. Check if the gene symbol "SHY1" matches the protein description above
  2. Verify the organism is correct: Saccharomyces cerevisiae (strain ATCC 204508 / S288c) (Baker's yeast).
  3. Check if protein family/domains align with what you find in literature
  4. If you find literature for a DIFFERENT gene with the same or similar symbol, STOP

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'SHY1' 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

Research Target:

Please provide a comprehensive research report on the gene SHY1 (gene ID: SHY1, UniProt: P53266) in yeast.

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.

Output

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.

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

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.

Target Gene/Protein Identity (from UniProt):

  • UniProt Accession: P53266
  • Protein Description: RecName: Full=Cytochrome oxidase assembly protein SHY1; AltName: Full=SURF1 homolog of Yeast; AltName: Full=SURF1-like protein;
  • Gene Information: Name=SHY1; OrderedLocusNames=YGR112W; ORFNames=G6150;
  • Organism (full): Saccharomyces cerevisiae (strain ATCC 204508 / S288c) (Baker's yeast).
  • Protein Family: Belongs to the SURF1 family. .
  • Key Domains: Surf1/Shy1. (IPR002994); Surf1/Surf4. (IPR045214); SURF1 (PF02104)

MANDATORY VERIFICATION STEPS:

  1. Check if the gene symbol "SHY1" matches the protein description above
  2. Verify the organism is correct: Saccharomyces cerevisiae (strain ATCC 204508 / S288c) (Baker's yeast).
  3. Check if protein family/domains align with what you find in literature
  4. If you find literature for a DIFFERENT gene with the same or similar symbol, STOP

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'SHY1' 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

Research Target:

Please provide a comprehensive research report on the gene SHY1 (gene ID: SHY1, UniProt: P53266) in yeast.

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.

Research Report: Saccharomyces cerevisiae SHY1 (UniProt P53266; ORF YGR112W) — Functional Annotation

Executive summary

SHY1 (YGR112W) encodes Shy1, a conserved SURF1-family mitochondrial inner membrane protein required for efficient cytochrome c oxidase (Complex IV; COX) biogenesis and respiratory competence in budding yeast. Genetic, biochemical, and complex-isolation studies support a model in which Shy1 acts during early Cox1 maturation/assembly, coordinating cofactor-center maturation (notably heme a3:CuB formation) with assembly intermediates, and coupling assembly status to Cox1 translational regulation via interaction with the Mss51/Cox14 regulatory module. (mick2007shy1couplescox1 pages 1-3, bestwick2010analysisofleigh pages 3-4)


1) Target verification (critical gene/protein identity)

1.1 Gene symbol and protein match

The literature explicitly identifies SHY1 as the yeast homolog of mammalian SURF1, and the gene cloned to complement respiration-deficient pet mutants is identical to ORF YGR112W; the gene was named SHY1 (Surf Homolog of Yeast). (mashkevich1997shy1theyeast pages 1-1)

1.2 Organism verification

The core primary literature establishing and characterizing Shy1 is in budding yeast (Saccharomyces cerevisiae), consistent with the UniProt organism context provided. (mashkevich1997shy1theyeast pages 1-1, mick2007shy1couplescox1 pages 1-1)

1.3 Family/domain/topology consistency

Shy1 is described as a conserved SURF1-family protein with two predicted transmembrane segments (near N- and C-termini) and mitochondrial targeting features, and it behaves as an intrinsic mitochondrial membrane protein in biochemical extraction assays. (mashkevich1997shy1theyeast pages 3-4, mashkevich1997shy1theyeast pages 7-7)

Sub-mitochondrial topology is consistent with an inner mitochondrial membrane (IMM) localization, with much of the polypeptide exposed to the intermembrane space (IMS). (mick2007shy1couplescox1 pages 1-3)

Conclusion: The SHY1 gene/protein studied in the cited literature matches the user-supplied UniProt entry P53266 (cytochrome oxidase assembly protein Shy1; SURF1 family) from S. cerevisiae. (mashkevich1997shy1theyeast pages 1-1, mick2007shy1couplescox1 pages 1-1)


2) Key concepts and definitions (current understanding)

2.1 What is SHY1?

SHY1 encodes an assembly factor (not a catalytic enzyme subunit) required for efficient formation of functional cytochrome c oxidase (COX/Complex IV) in mitochondria. Loss of SHY1 decreases assembled complex IV abundance/activity and impairs respiratory growth. (nijtmans2001shy1poccursin pages 1-2, mick2007shy1couplescox1 pages 1-3)

2.2 What is cytochrome c oxidase (Complex IV) assembly?

Complex IV is the terminal oxidase of the respiratory chain, and its biogenesis requires stepwise assembly of mitochondria-encoded and nuclear-encoded subunits plus cofactor-center maturation (e.g., heme and copper centers). Shy1/SURF1-family proteins are implicated at the stage of Cox1 maturation, where formation of the heme a3:CuB catalytic center is a critical step. (bestwick2010analysisofleigh pages 3-4, stiburek2009theroleof pages 23-26)

2.3 “Coupling translation to assembly” for Cox1

In yeast, Cox1 synthesis is regulated by feedback mechanisms in which the translational activator Mss51 is sequestered in assembly intermediates when downstream assembly is blocked. Shy1 physically associates with Mss51 and Cox14, and thereby is positioned to link Cox1 synthesis regulation to Cox1 maturation/assembly progress. (mick2007shy1couplescox1 pages 1-3, reinhold2011mimickingasurf1 pages 2-3)


3) Molecular function and mechanism (experimental evidence)

3.1 Localization and physical state

  • Mitochondrial/IMM localization: Antibody-based localization and biochemical fractionation support Shy1 as a mitochondrial inner membrane protein. (mashkevich1997shy1theyeast pages 1-1, mick2007shy1couplescox1 pages 1-3)
  • Integral membrane behavior: Shy1 is not extracted by high-salt and requires detergent, consistent with an integral membrane protein. (mashkevich1997shy1theyeast pages 7-7)
  • Higher-order complexes: Shy1 occurs in high-molecular-weight complexes (reported ~250 kDa) consistent with protein–protein interactions relevant to assembly. (nijtmans2001shy1poccursin pages 1-2)

3.2 Role in Complex IV biogenesis and Cox1 maturation

Multiple lines of evidence indicate Shy1 is required for efficient Complex IV assembly:
- Disruption of SHY1 strongly reduces steady-state assembled COX to ~30% of control, yet remaining assembled COX can appear enzymatically normal. (nijtmans2001shy1poccursin pages 1-2)
- Shy1 mediates formation of the heme a3:CuB center in Cox1 (a key catalytic cofactor center), and mutations in Shy1 can cause impaired Cox1 “hemylation” and changes in copper-related phenotypes. (bestwick2010analysisofleigh pages 3-4, bestwick2010analysisofleigh pages 1-2)

Mechanistic proposals (with experimental anchoring):
- Shy1/SURF1 has been proposed to function as a heme insertase or as a chaperone maintaining Cox1 competent for heme insertion; loss of SURF1 leads to accumulation of assembly intermediates. (reinhold2011mimickingasurf1 pages 2-3)
- Comparative evidence summarized in authoritative synthesis suggests bacterial Surf1 homologs can bind heme a in vivo and are implicated in heme insertion/stabilization for terminal oxidase biogenesis, supporting a conserved biochemical theme for the family (but direct heme-binding by yeast Shy1 is not demonstrated in the provided excerpts). (stiburek2009theroleof pages 23-26)

3.3 Coupling to Cox1 translational regulation

Shy1 is not merely a static assembly factor: it participates in regulatory complexes that couple Cox1 synthesis and assembly state.
- Shy1 associates with the Cox1 translational regulators Mss51 and Cox14, forming complexes that connect translational regulation to early assembly. (mick2007shy1couplescox1 pages 1-3)
- Patient-mutation–mimicking Shy1 alleles demonstrate that COX assembly can be uncoupled from translational feedback: e.g., a Shy1 mutant can accumulate in ~200 kDa intermediates and bypass feedback control on Cox1 expression but still block later assembly steps, revealing separable functional contributions. (reinhold2011mimickingasurf1 pages 1-2, reinhold2011mimickingasurf1 pages 10-11)


4) Pathway context: where SHY1 acts

4.1 Biological process / pathway placement

SHY1 functions in the mitochondrial oxidative phosphorylation (OXPHOS) biogenesis pathway, specifically in Complex IV assembly, acting at or near the Cox1 maturation stage and influencing formation of later supercomplexes containing Complex III and IV. (mick2007shy1couplescox1 pages 1-1, mick2007shy1couplescox1 pages 1-3)

4.2 Interaction with respiratory supercomplex formation

Shy1-containing assembly intermediates can associate with other respiratory complexes:
- Purification and complex-association evidence supports Shy1 association with respiratory chain complexes III/IV and transitional supercomplex states. (mick2007shy1couplescox1 pages 1-3, mick2007shy1couplescox1 pages 1-1)
- In a 2024 fission yeast study (see §5), the SURF1 homolog also co-immunoprecipitates with a complex III subunit and BN-PAGE supports links to supercomplex biology, supporting conserved network positioning of SURF1-family proteins. (luo2024characterizationofshy1 pages 11-13, luo2024characterizationofshy1 pages 1-2)


5) Recent developments (prioritizing 2023–2024)

Yeast SHY1 literature is foundational (1997–2011), but 2024 work updates the field with cross-yeast comparative and interaction-network evidence relevant to SURF1-family mechanistic questions.

5.1 2024: Functional characterization of SURF1 homolog in fission yeast (S. pombe)

A 2024 primary study characterized Shy1 in Schizosaccharomyces pombe as a SURF1-domain IMM protein with two transmembrane segments and reported:
- Physical interactions with complex IV subunits and assembly factors; co-immunoprecipitation of a complex III subunit (Rip1) suggested involvement in III–IV supercomplex associations. (luo2024characterizationofshy1 pages 1-2, luo2024characterizationofshy1 pages 11-13)
- BN-PAGE evidence that complex IV abundance is diminished in ∆shy1 strains. (luo2024characterizationofshy1 pages 1-2)
- An interaction network linking Shy1 to Cox1-related factors (including Mss51), copper chaperones, and heme-related factors such as Cox10/Cox11 homologs (interaction scores in their Table 1). (luo2024characterizationofshy1 pages 6-10)

Interpretation for S. cerevisiae SHY1 annotation: While organism-specific compensatory effects exist in S. pombe, these data reinforce that SURF1-family proteins sit at a conserved nexus connecting Cox1 expression/maturation, cofactor insertion pathways, and respiratory complex organization. (luo2024characterizationofshy1 pages 11-13, luo2024characterizationofshy1 pages 6-10)


6) Current applications and real-world implementations

6.1 Yeast as a model for human SURF1 disease variants

Because SURF1 mutations are a frequent cause of Leigh syndrome, yeast SHY1 has been used as an experimentally tractable model to test pathogenic mechanisms of SURF1 alleles.
- Mimicking specific patient alleles in yeast revealed separable roles for SURF1/Shy1 in assembly progression vs translational coupling, and highlighted how variants can cause turnover defects or accumulation in specific assembly intermediates. (reinhold2011mimickingasurf1 pages 1-2, reinhold2011mimickingasurf1 pages 10-11)

6.2 Genetic suppression and pathway probing

SHY1 mutant phenotypes can be modified by nuclear genetic changes or transcriptional activators.
- Nuclear revertants can increase assembled COX by ~4–5× and restore respiration to ~78% of wild type, supporting the concept that upstream expression/biogenesis capacity can buffer COX assembly defects. (barrientos2002shy1pisnecessary pages 1-2, barrientos2002shy1pisnecessary pages 2-3)
- Overexpression of transcriptional activators (HAP-related) can partially rescue respiration and strongly improve generation time on non-fermentable carbon sources (e.g., HAP4 high-copy suppression). (fontanesi2008transcriptionalactivatorshapnfy pages 2-4)


7) Quantitative phenotype summary (statistics/data)

The following table consolidates key quantitative measures from primary studies (COX activities, respiration rates, inhibitor sensitivities, and growth rates).

Study (author year, journal) Strain/allele Assay/metric Result (include numeric values and units or %) Interpretation
Mashkevich 1997, J Biol Chem Wild type (W303-1A) Cytochrome c oxidase activity 1.72 (table units) (mashkevich1997shy1theyeast pages 3-4, mashkevich1997shy1theyeast media c0394742) Reference wild-type COX activity
Mashkevich 1997, J Biol Chem W125 Cytochrome c oxidase activity 1.32 (~77% of WT) (mashkevich1997shy1theyeast pages 3-4, mashkevich1997shy1theyeast media c0394742) Partial COX deficiency
Mashkevich 1997, J Biol Chem C173/U1 Cytochrome c oxidase activity 1.04 (~60% of WT) (mashkevich1997shy1theyeast pages 3-4, mashkevich1997shy1theyeast media c0394742) Partial COX deficiency
Mashkevich 1997, J Biol Chem W303ΔSHY1(H) Cytochrome c oxidase activity 1.29 (~75% of WT) (mashkevich1997shy1theyeast pages 3-4, mashkevich1997shy1theyeast media c0394742) Partial reduction in COX activity
Mashkevich 1997, J Biol Chem W303ΔSHY1(U) Cytochrome c oxidase activity 0.67 (~39% of WT) (mashkevich1997shy1theyeast pages 3-4, mashkevich1997shy1theyeast media c0394742) Stronger COX defect
Mashkevich 1997, J Biol Chem Wild type (W303-1A) NADH oxidase 1.11 (table units) (mashkevich1997shy1theyeast pages 3-4, mashkevich1997shy1theyeast media c0394742) Reference wild-type respiratory activity
Mashkevich 1997, J Biol Chem W125 NADH oxidase 0.33 (~30% of WT); text states 30% of wild-type NADH oxidase activity (mashkevich1997shy1theyeast pages 3-4, mashkevich1997shy1theyeast media c0394742) Severe respiratory impairment despite residual activity
Mashkevich 1997, J Biol Chem C173/U1 NADH oxidase 0.18 (~16% of WT) (mashkevich1997shy1theyeast pages 3-4, mashkevich1997shy1theyeast media c0394742) Severe respiratory impairment
Mashkevich 1997, J Biol Chem W303ΔSHY1(H) NADH oxidase 1.09 (~98% of WT) (mashkevich1997shy1theyeast pages 3-4, mashkevich1997shy1theyeast media c0394742) Near-normal NADH oxidase despite COX reduction
Mashkevich 1997, J Biol Chem W303ΔSHY1(U) NADH oxidase 0.21 (~19% of WT); text states 20% of wild-type NADH oxidase activity (mashkevich1997shy1theyeast pages 3-4, mashkevich1997shy1theyeast media c0394742) Strong respiratory defect; no appreciable growth on glycerol or ethanol
Mashkevich 1997, J Biol Chem Wild type and shy1-related strains ATPase activity ≈5.6–6.6 across strains (mashkevich1997shy1theyeast pages 3-4, mashkevich1997shy1theyeast media c0394742) ATPase largely unaffected relative to respiratory defects
Nijtmans 2001, FEBS Lett shy1 disruptant/null Assembled cytochrome c oxidase Approximately 30% of control (nijtmans2001shy1poccursin pages 1-2) SHY1 is required for efficient COX assembly, but some holo-COX remains
Nijtmans 2001, FEBS Lett Shy1p complex Apparent complex size About 250 kDa (nijtmans2001shy1poccursin pages 1-2) Shy1p occurs in a higher-molecular-weight assembly-associated complex
Barrientos 2002, EMBO J shy1 mutants Fully assembled and functional COX ~10±15% (barrientos2002shy1pisnecessary pages 1-2) Severe COX deficiency in shy1 mutants
Barrientos 2002, EMBO J DSHY1 (shy1 null) Whole-cell respiration rate ~20% of wild type (barrientos2002shy1pisnecessary pages 1-2, barrientos2002shy1pisnecessary pages 2-3) Major respiratory defect
Barrientos 2002, EMBO J DSHY1 (shy1 null) Inhibitor sensitivity of residual respiration 59% inhibition by antimycin A; 93% inhibition by KCN (barrientos2002shy1pisnecessary pages 1-2, barrientos2002shy1pisnecessary pages 2-3) Residual respiration still largely mitochondrial/COX-linked
Barrientos 2002, EMBO J Nuclear revertant of DSHY1 Whole-cell respiration rate 78% of wild type (barrientos2002shy1pisnecessary pages 1-2, barrientos2002shy1pisnecessary pages 2-3) Suppression strongly restores respiratory function
Barrientos 2002, EMBO J DSHY1 mitochondria NADH oxidation 14% of wild type (barrientos2002shy1pisnecessary pages 2-3) Mitochondrial respiratory chain severely compromised
Barrientos 2002, EMBO J Revertant mitochondria NADH oxidation ~60% of wild type (barrientos2002shy1pisnecessary pages 2-3) Partial biochemical rescue
Barrientos 2002, EMBO J Revertant mitochondria COX specific activity ~4-fold higher than mutant; 37–40% of wild type (barrientos2002shy1pisnecessary pages 2-3) Suppression improves COX abundance/activity but not fully to WT
Barrientos 2002, EMBO J Wild type vs mutant P/O ratio 1.31 (wild type) vs 1.17 (mutant) (barrientos2002shy1pisnecessary pages 2-3) Oxidative phosphorylation efficiency only modestly reduced relative to respiration defect
Barrientos 2002, EMBO J Wild type Doubling time on glycerol 2.4 h (barrientos2002shy1pisnecessary pages 2-3) Baseline respiratory growth
Barrientos 2002, EMBO J Revertant Doubling time on glycerol 3.3 h (barrientos2002shy1pisnecessary pages 2-3) Near-wild-type respiratory growth restored
Barrientos 2002, EMBO J Mutant Doubling time on glycerol 28 h (barrientos2002shy1pisnecessary pages 2-3) Severe respiratory growth defect
Fontanesi 2008, Hum Mol Genet shy1 mutant Generation time in ethanol–glycerol 28 h (fontanesi2008transcriptionalactivatorshapnfy pages 2-4) Confirms severe non-fermentable growth defect
Fontanesi 2008, Hum Mol Genet Wild type Generation time in ethanol–glycerol 2.4 h (fontanesi2008transcriptionalactivatorshapnfy pages 2-4) Reference respiratory growth
Fontanesi 2008, Hum Mol Genet shy1 mutant + HAP4 high-copy Generation time in ethanol–glycerol 4.2 h (fontanesi2008transcriptionalactivatorshapnfy pages 2-4) HAP4 strongly suppresses shy1 respiratory growth defect
Fontanesi 2008, Hum Mol Genet shy1 null KCN-sensitive endogenous respiration Increased from 15% to 20% of wild type with HAP2 overexpression (fontanesi2008transcriptionalactivatorshapnfy pages 2-4) HAP2 partially suppresses respiratory defect
Fontanesi 2008, Hum Mol Genet W125 point mutant KCN-sensitive endogenous respiration Increased from 18% to 25% of wild type with HAP2 overexpression (fontanesi2008transcriptionalactivatorshapnfy pages 2-4) HAP2 partially suppresses point-mutant respiratory defect
Fontanesi 2008, Hum Mol Genet HAP4 expression HAP4 mRNA regulation 4–5-fold higher mRNA on lactate vs glucose (fontanesi2008transcriptionalactivatorshapnfy pages 2-4) Carbon-responsive transcription likely contributes to suppression context

Table: This table compiles numeric phenotypes reported for Saccharomyces cerevisiae shy1 mutants and suppressors across key studies, including enzyme activities, respiration, COX assembly, inhibitor sensitivity, and growth rates. It is useful for quickly comparing the severity of SHY1 loss and the extent of genetic suppression.

A key visual source for the enzyme activity dataset is the original Table II from Mashkevich et al. (1997). (mashkevich1997shy1theyeast media c0394742)


8) Expert interpretation and current consensus

8.1 Consensus function

Across independent studies, SHY1 is best annotated as a mitochondrial inner membrane Complex IV assembly factor acting during Cox1 maturation/early assembly, with strong evidence for participation in the formation of the heme a3:CuB catalytic center and in coordinating assembly with translation control. (bestwick2010analysisofleigh pages 3-4, mick2007shy1couplescox1 pages 1-3)

8.2 What remains unresolved

Even with strong genetic/biochemical evidence, the precise biochemical action of Shy1 remains incompletely resolved in the provided sources: whether Shy1 directly binds/transfers heme a/a3, acts as a scaffold/chaperone for Cox1 conformational maturation, or mainly regulates/co-localizes cofactor insertion machinery is still under investigation. This uncertainty is explicitly reflected in mechanistic framing and cross-species summaries. (reinhold2011mimickingasurf1 pages 2-3, stiburek2009theroleof pages 23-26)


Appendix: Core sources with publication dates and URLs

  • Mashkevich et al., May 1997, J Biol Chem: https://doi.org/10.1074/jbc.272.22.14356 (mashkevich1997shy1theyeast pages 1-1)
  • Nijtmans et al., Jun 2001, FEBS Letters: https://doi.org/10.1016/S0014-5793(01)02447-4 (nijtmans2001shy1poccursin pages 1-2)
  • Barrientos et al., Jan 2002, EMBO J: https://doi.org/10.1093/emboj/21.1.43 (barrientos2002shy1pisnecessary pages 1-2)
  • Mick et al., Oct 2007, EMBO J: https://doi.org/10.1038/sj.emboj.7601862 (mick2007shy1couplescox1 pages 1-3)
  • Fontanesi et al., Mar 2008, Hum Mol Genet: https://doi.org/10.1093/hmg/ddm349 (fontanesi2008transcriptionalactivatorshapnfy pages 2-4)
  • Bestwick et al., Sep 2010, Mol Cell Biol: https://doi.org/10.1128/MCB.00228-10 (bestwick2010analysisofleigh pages 3-4)
  • Reinhold et al., Jun 2011, Hum Mol Genet: https://doi.org/10.1093/hmg/ddr145 (reinhold2011mimickingasurf1 pages 1-2)
  • Luo et al., Sep 2024, Scientific Reports (S. pombe Shy1 homolog): https://doi.org/10.1038/s41598-024-72681-9 (luo2024characterizationofshy1 pages 1-2)

References

  1. (mick2007shy1couplescox1 pages 1-3): David U Mick, Karina Wagner, Martin van der Laan, Ann E Frazier, Inge Perschil, Magdalena Pawlas, Helmut E Meyer, Bettina Warscheid, and Peter Rehling. Shy1 couples cox1 translational regulation to cytochrome c oxidase assembly. The EMBO Journal, 26:4347-4358, Oct 2007. URL: https://doi.org/10.1038/sj.emboj.7601862, doi:10.1038/sj.emboj.7601862. This article has 173 citations.

  2. (bestwick2010analysisofleigh pages 3-4): Megan Bestwick, Mi-Young Jeong, Oleh Khalimonchuk, Hyung Kim, and Dennis R. Winge. Analysis of leigh syndrome mutations in the yeast surf1 homolog reveals a new member of the cytochrome oxidase assembly factor family. Molecular and Cellular Biology, 30:4480-4491, Sep 2010. URL: https://doi.org/10.1128/mcb.00228-10, doi:10.1128/mcb.00228-10. This article has 48 citations and is from a domain leading peer-reviewed journal.

  3. (mashkevich1997shy1theyeast pages 1-1): Grigoriy Mashkevich, Barbara Repetto, D. Moira Glerum, Can Jin, and Alexander Tzagoloff. Shy1, the yeast homolog of the mammaliansurf-1 gene, encodes a mitochondrial protein required for respiration*. The Journal of Biological Chemistry, 272:14356-14364, May 1997. URL: https://doi.org/10.1074/jbc.272.22.14356, doi:10.1074/jbc.272.22.14356. This article has 175 citations.

  4. (mick2007shy1couplescox1 pages 1-1): David U Mick, Karina Wagner, Martin van der Laan, Ann E Frazier, Inge Perschil, Magdalena Pawlas, Helmut E Meyer, Bettina Warscheid, and Peter Rehling. Shy1 couples cox1 translational regulation to cytochrome c oxidase assembly. The EMBO Journal, 26:4347-4358, Oct 2007. URL: https://doi.org/10.1038/sj.emboj.7601862, doi:10.1038/sj.emboj.7601862. This article has 173 citations.

  5. (mashkevich1997shy1theyeast pages 3-4): Grigoriy Mashkevich, Barbara Repetto, D. Moira Glerum, Can Jin, and Alexander Tzagoloff. Shy1, the yeast homolog of the mammaliansurf-1 gene, encodes a mitochondrial protein required for respiration*. The Journal of Biological Chemistry, 272:14356-14364, May 1997. URL: https://doi.org/10.1074/jbc.272.22.14356, doi:10.1074/jbc.272.22.14356. This article has 175 citations.

  6. (mashkevich1997shy1theyeast pages 7-7): Grigoriy Mashkevich, Barbara Repetto, D. Moira Glerum, Can Jin, and Alexander Tzagoloff. Shy1, the yeast homolog of the mammaliansurf-1 gene, encodes a mitochondrial protein required for respiration*. The Journal of Biological Chemistry, 272:14356-14364, May 1997. URL: https://doi.org/10.1074/jbc.272.22.14356, doi:10.1074/jbc.272.22.14356. This article has 175 citations.

  7. (nijtmans2001shy1poccursin pages 1-2): L.G.J. Nijtmans, M. Artal Sanz, M. Bucko, M.H. Farhoud, M. Feenstra, G.A.J. Hakkaart, M. Zeviani, and L.A. Grivell. Shy1p occurs in a high molecular weight complex and is required for efficient assembly of cytochrome c oxidase in yeast. FEBS Letters, 498:46-51, Jun 2001. URL: https://doi.org/10.1016/s0014-5793(01)02447-4, doi:10.1016/s0014-5793(01)02447-4. This article has 89 citations and is from a peer-reviewed journal.

  8. (stiburek2009theroleof pages 23-26): L Stibůrek. The role of human sco1, sco2, surf1 and oxa1l in the biogenesis of the mitochondrial oxidative phosphorylation system. Unknown journal, 2009.

  9. (reinhold2011mimickingasurf1 pages 2-3): Robert Reinhold, Bettina Bareth, Martina Balleininger, Mirjam Wissel, Peter Rehling, and David U. Mick. Mimicking a surf1 allele reveals uncoupling of cytochrome c oxidase assembly from translational regulation in yeast. Human molecular genetics, 20 12:2379-93, Jun 2011. URL: https://doi.org/10.1093/hmg/ddr145, doi:10.1093/hmg/ddr145. This article has 28 citations and is from a domain leading peer-reviewed journal.

  10. (bestwick2010analysisofleigh pages 1-2): Megan Bestwick, Mi-Young Jeong, Oleh Khalimonchuk, Hyung Kim, and Dennis R. Winge. Analysis of leigh syndrome mutations in the yeast surf1 homolog reveals a new member of the cytochrome oxidase assembly factor family. Molecular and Cellular Biology, 30:4480-4491, Sep 2010. URL: https://doi.org/10.1128/mcb.00228-10, doi:10.1128/mcb.00228-10. This article has 48 citations and is from a domain leading peer-reviewed journal.

  11. (reinhold2011mimickingasurf1 pages 1-2): Robert Reinhold, Bettina Bareth, Martina Balleininger, Mirjam Wissel, Peter Rehling, and David U. Mick. Mimicking a surf1 allele reveals uncoupling of cytochrome c oxidase assembly from translational regulation in yeast. Human molecular genetics, 20 12:2379-93, Jun 2011. URL: https://doi.org/10.1093/hmg/ddr145, doi:10.1093/hmg/ddr145. This article has 28 citations and is from a domain leading peer-reviewed journal.

  12. (reinhold2011mimickingasurf1 pages 10-11): Robert Reinhold, Bettina Bareth, Martina Balleininger, Mirjam Wissel, Peter Rehling, and David U. Mick. Mimicking a surf1 allele reveals uncoupling of cytochrome c oxidase assembly from translational regulation in yeast. Human molecular genetics, 20 12:2379-93, Jun 2011. URL: https://doi.org/10.1093/hmg/ddr145, doi:10.1093/hmg/ddr145. This article has 28 citations and is from a domain leading peer-reviewed journal.

  13. (luo2024characterizationofshy1 pages 11-13): Ying Luo, Yuanqi Xu, Fawad Ahmad, Gang Feng, and Ying Huang. Characterization of shy1, the schizosaccharomyces pombe homolog of human surf1. Scientific Reports, Sep 2024. URL: https://doi.org/10.1038/s41598-024-72681-9, doi:10.1038/s41598-024-72681-9. This article has 8 citations and is from a peer-reviewed journal.

  14. (luo2024characterizationofshy1 pages 1-2): Ying Luo, Yuanqi Xu, Fawad Ahmad, Gang Feng, and Ying Huang. Characterization of shy1, the schizosaccharomyces pombe homolog of human surf1. Scientific Reports, Sep 2024. URL: https://doi.org/10.1038/s41598-024-72681-9, doi:10.1038/s41598-024-72681-9. This article has 8 citations and is from a peer-reviewed journal.

  15. (luo2024characterizationofshy1 pages 6-10): Ying Luo, Yuanqi Xu, Fawad Ahmad, Gang Feng, and Ying Huang. Characterization of shy1, the schizosaccharomyces pombe homolog of human surf1. Scientific Reports, Sep 2024. URL: https://doi.org/10.1038/s41598-024-72681-9, doi:10.1038/s41598-024-72681-9. This article has 8 citations and is from a peer-reviewed journal.

  16. (barrientos2002shy1pisnecessary pages 1-2): A. Barrientos, D. Korr, and A. Tzagoloff. Shy1p is necessary for full expression of mitochondrial cox1 in the yeast model of leigh's syndrome. The EMBO Journal, 21:43-52, Jan 2002. URL: https://doi.org/10.1093/emboj/21.1.43, doi:10.1093/emboj/21.1.43. This article has 210 citations.

  17. (barrientos2002shy1pisnecessary pages 2-3): A. Barrientos, D. Korr, and A. Tzagoloff. Shy1p is necessary for full expression of mitochondrial cox1 in the yeast model of leigh's syndrome. The EMBO Journal, 21:43-52, Jan 2002. URL: https://doi.org/10.1093/emboj/21.1.43, doi:10.1093/emboj/21.1.43. This article has 210 citations.

  18. (fontanesi2008transcriptionalactivatorshapnfy pages 2-4): Flavia Fontanesi, Can Jin, Alexander Tzagoloff, and Antoni Barrientos. Transcriptional activators hap/nf-y rescue a cytochrome c oxidase defect in yeast and human cells. Human molecular genetics, 17 6:775-88, Mar 2008. URL: https://doi.org/10.1093/hmg/ddm349, doi:10.1093/hmg/ddm349. This article has 67 citations and is from a domain leading peer-reviewed journal.

  19. (mashkevich1997shy1theyeast media c0394742): Grigoriy Mashkevich, Barbara Repetto, D. Moira Glerum, Can Jin, and Alexander Tzagoloff. Shy1, the yeast homolog of the mammaliansurf-1 gene, encodes a mitochondrial protein required for respiration*. The Journal of Biological Chemistry, 272:14356-14364, May 1997. URL: https://doi.org/10.1074/jbc.272.22.14356, doi:10.1074/jbc.272.22.14356. This article has 175 citations.

Citations

  1. stiburek2009theroleof pages 23-26
  2. fontanesi2008transcriptionalactivatorshapnfy pages 2-4
  3. bestwick2010analysisofleigh pages 3-4
  4. bestwick2010analysisofleigh pages 1-2
  5. https://doi.org/10.1074/jbc.272.22.14356
  6. https://doi.org/10.1016/S0014-5793(01
  7. https://doi.org/10.1093/emboj/21.1.43
  8. https://doi.org/10.1038/sj.emboj.7601862
  9. https://doi.org/10.1093/hmg/ddm349
  10. https://doi.org/10.1128/MCB.00228-10
  11. https://doi.org/10.1093/hmg/ddr145
  12. https://doi.org/10.1038/s41598-024-72681-9
  13. https://doi.org/10.1038/sj.emboj.7601862,
  14. https://doi.org/10.1128/mcb.00228-10,
  15. https://doi.org/10.1074/jbc.272.22.14356,
  16. https://doi.org/10.1016/s0014-5793(01
  17. https://doi.org/10.1093/hmg/ddr145,
  18. https://doi.org/10.1038/s41598-024-72681-9,
  19. https://doi.org/10.1093/emboj/21.1.43,
  20. https://doi.org/10.1093/hmg/ddm349,

📄 View Raw YAML

id: P53266
gene_symbol: SHY1
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:559292
  label: Saccharomyces cerevisiae
description: >-
  SHY1 encodes the yeast SURF1-family cytochrome c oxidase assembly factor.
  Shy1 is an intrinsic mitochondrial inner membrane protein required for
  efficient complex IV biogenesis, acting during early Cox1 maturation and
  coupling Cox1 translational regulation by the Mss51/Cox14 module to
  downstream complex IV assembly. Shy1 is not a mature cytochrome c oxidase
  subunit and is not a general unfolded-protein chaperone; its core role is
  assembly of mitochondrial respiratory chain complex IV.
existing_annotations:
- term:
    id: GO:0033617
    label: mitochondrial respiratory chain complex IV assembly
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      The PANTHER/IBA annotation is consistent with direct yeast evidence and
      conserved SURF1-family biology. Shy1 is repeatedly shown to be required
      for efficient cytochrome c oxidase assembly and Cox1 maturation.
    action: ACCEPT
    reason: Core biological process for SHY1.
    supported_by:
    - reference_id: PMID:17882259
      supporting_text: "Shy1 is an assembly factor for complex IV in Saccharomyces cerevisiae"
    - reference_id: file:yeast/SHY1/SHY1-deep-research-falcon.md
      supporting_text: Falcon deep research identifies SHY1 as a SURF1-family mitochondrial inner membrane complex IV assembly factor.
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      Mitochondrial localization is correct for Shy1. The more specific
      mitochondrial inner membrane term is also present, but the broader
      mitochondrion annotation is supported by direct studies and family
      transfer.
    action: ACCEPT
    reason: Shy1 performs its assembly-factor function in mitochondria.
    supported_by:
    - reference_id: PMID:9162072
      supporting_text: "An antibody against the carboxyl-terminal half of Shy1p has been used to localize the protein in the inner mitochondrial membrane."
- term:
    id: GO:0005743
    label: mitochondrial inner membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  review:
    summary: >-
      UniProt subcellular-location mapping to mitochondrial inner membrane is
      accurate and agrees with direct localization experiments.
    action: ACCEPT
    reason: Core localization for Shy1.
    supported_by:
    - reference_id: PMID:9162072
      supporting_text: "An antibody against the carboxyl-terminal half of Shy1p has been used to localize the protein in the inner mitochondrial membrane."
- term:
    id: GO:0016020
    label: membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  review:
    summary: >-
      InterPro transfer to the generic membrane term is directionally correct
      for a SURF1-family membrane protein but too broad for this curated review.
      Shy1 is specifically an inner mitochondrial membrane protein.
    action: MODIFY
    reason: Replace generic membrane with the experimentally supported mitochondrial inner membrane location.
    proposed_replacement_terms:
    - id: GO:0005743
      label: mitochondrial inner membrane
    supported_by:
    - reference_id: PMID:9162072
      supporting_text: "An antibody against the carboxyl-terminal half of Shy1p has been used to localize the protein in the inner mitochondrial membrane."
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:17882259
  review:
    summary: >-
      Shy1 interactions with Cox14, Mss51, Coa1 and complex IV assembly
      intermediates are central to its biology, but the generic protein binding
      term is not informative. The functional consequence is complex IV assembly
      rather than protein binding as a standalone molecular function.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      Use complex IV assembly and mitochondrial inner membrane annotations
      instead of generic protein binding.
    supported_by:
    - reference_id: PMID:17882259
      supporting_text: "Shy1 interacts with Mss51 and Cox14, translational regulators of Cox1."
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:17882260
  review:
    summary: >-
      The Coa1/Shy1 interaction supports the assembly pathway model but does not
      justify retaining a generic protein binding MF annotation.
    action: MARK_AS_OVER_ANNOTATED
    reason: The interaction is better represented as part of complex IV assembly.
    supported_by:
    - reference_id: PMID:17882260
      supporting_text: "The interaction between Coa1 and Cox1, and the physical and genetic interactions between Coa1 and Mss51, Shy1 and Cox14 suggest that Coa1 coordinates the transition"
- term:
    id: GO:0016020
    label: membrane
  evidence_type: IDA
  original_reference_id: PMID:15306853
  review:
    summary: >-
      The direct membrane annotation is valid but less specific than the
      mitochondrial inner membrane annotations supported by SHY1 localization and
      function.
    action: MODIFY
    reason: Use the specific inner mitochondrial membrane component term.
    proposed_replacement_terms:
    - id: GO:0005743
      label: mitochondrial inner membrane
    supported_by:
    - reference_id: PMID:9162072
      supporting_text: "An antibody against the carboxyl-terminal half of Shy1p has been used to localize the protein in the inner mitochondrial membrane."
- term:
    id: GO:0005777
    label: peroxisome
  evidence_type: HDA
  original_reference_id: PMID:35563734
  review:
    summary: >-
      Retain as non-core only. The canonical and mechanistic Shy1 localization is
      the mitochondrial inner membrane. The peroxisome annotation comes from a
      high-throughput peroxisomal screen and has no demonstrated role in Shy1's
      complex IV assembly function.
    action: KEEP_AS_NON_CORE
    reason: Possible context-specific or high-throughput localization, not the core functional location.
    supported_by:
    - reference_id: PMID:35563734
      supporting_text: "we used a high-throughput screen to discover peroxisomal proteins in yeast."
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: HDA
  original_reference_id: PMID:24769239
  review:
    summary: >-
      High-throughput mitochondrial proteomics detection is consistent with
      Shy1's established mitochondrial role.
    action: ACCEPT
    reason: Correct broad mitochondrial localization.
    supported_by:
    - reference_id: PMID:24769239
      supporting_text: "we performed an overall quantitative proteomic and phosphoproteomic study of isolated mitochondria extracted from yeast grown on fermentative (glucose or galactose) and respiratory (lactate) media"
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: HDA
  original_reference_id: PMID:16823961
  review:
    summary: >-
      Mitochondrial proteome detection is consistent with Shy1's canonical
      localization and function.
    action: ACCEPT
    reason: Correct broad mitochondrial localization.
    supported_by:
    - reference_id: PMID:16823961
      supporting_text: "A total of 851 different proteins (PROMITO dataset) were identified by use of multidimensional LC-MS/MS, 1D-SDS-PAGE combined with nano-LC-MS/MS and 2D-PAGE"
- term:
    id: GO:0005743
    label: mitochondrial inner membrane
  evidence_type: IDA
  original_reference_id: PMID:15306853
  review:
    summary: >-
      Inner mitochondrial membrane localization is appropriate for Shy1's role in
      Cox1 maturation and complex IV assembly.
    action: ACCEPT
    reason: Core cellular component for Shy1 function.
    supported_by:
    - reference_id: PMID:15306853
      supporting_text: "The release of Mss51p from the complex occurs at a downstream step in the assembly pathway, probably catalyzed by Shy1p."
- term:
    id: GO:0005743
    label: mitochondrial inner membrane
  evidence_type: IDA
  original_reference_id: PMID:9162072
  review:
    summary: >-
      The original SHY1 characterization directly localized Shy1 to the inner
      mitochondrial membrane.
    action: ACCEPT
    reason: Direct localization evidence for the core site of action.
    supported_by:
    - reference_id: PMID:9162072
      supporting_text: "An antibody against the carboxyl-terminal half of Shy1p has been used to localize the protein in the inner mitochondrial membrane."
- term:
    id: GO:0033617
    label: mitochondrial respiratory chain complex IV assembly
  evidence_type: IMP
  original_reference_id: PMID:17882259
  review:
    summary: >-
      Strong mutant and biochemical evidence supports Shy1 as a complex IV
      assembly factor that links Cox1 translational control with assembly
      intermediate progression.
    action: ACCEPT
    reason: Core biological process supported by direct experimental evidence.
    supported_by:
    - reference_id: PMID:17882259
      supporting_text: "We suggest that Shy1 links Cox1 translational regulation to complex IV assembly and supercomplex formation."
- term:
    id: GO:0051082
    label: unfolded protein binding
  evidence_type: IMP
  original_reference_id: PMID:11389896
  review:
    summary: >-
      The evidence shows that Shy1 occurs in an assembly-associated complex and
      is required for efficient cytochrome c oxidase assembly. It does not show
      general unfolded-protein binding or a broad chaperone substrate range.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      The annotation over-interprets an assembly-factor phenotype. Shy1 should be
      curated to complex IV assembly rather than generic unfolded protein binding.
    supported_by:
    - reference_id: PMID:11389896
      supporting_text: "Shy1p may either facilitate assembly of the enzyme, or increase its stability."
- term:
    id: GO:0005743
    label: mitochondrial inner membrane
  evidence_type: IDA
  original_reference_id: PMID:9162072
  review:
    summary: >-
      Duplicate direct UniProt annotation for Shy1 inner mitochondrial membrane
      localization; retain because it accurately reflects the original
      experimental localization.
    action: ACCEPT
    reason: Direct localization evidence for the core site of action.
    supported_by:
    - reference_id: PMID:9162072
      supporting_text: "An antibody against the carboxyl-terminal half of Shy1p has been used to localize the protein in the inner mitochondrial membrane."
references:
- id: GO_REF:0000002
  title: Gene Ontology annotation through association of InterPro records with GO terms
  findings: []
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings: []
- id: GO_REF:0000044
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt
  findings: []
- id: PMID:11389896
  title: Shy1p occurs in a high molecular weight complex and is required for efficient assembly of cytochrome c oxidase in yeast.
  findings:
  - statement: Shy1 is required for efficient complex IV assembly but residual normal enzyme can still form.
    supporting_text: "Steady-state levels of the enzyme were found to be strongly reduced, the total amount of assembled complex being approximately 30% of control."
- id: PMID:15306853
  title: Mss51p and Cox14p jointly regulate mitochondrial Cox1p expression in Saccharomyces cerevisiae.
  findings:
  - statement: Shy1 likely acts downstream of the Cox14-Cox1-Mss51 regulatory complex.
    supporting_text: "The release of Mss51p from the complex occurs at a downstream step in the assembly pathway, probably catalyzed by Shy1p."
- id: PMID:16823961
  title: 'Toward the complete yeast mitochondrial proteome: multidimensional separation techniques for mitochondrial proteomics.'
  findings: []
- id: PMID:17882259
  title: Shy1 couples Cox1 translational regulation to cytochrome c oxidase assembly.
  findings:
  - statement: Shy1 is a complex IV assembly factor that interacts with Cox1 translational regulators and assembly intermediates.
    supporting_text: "Shy1 interacts with Mss51 and Cox14, translational regulators of Cox1."
- id: PMID:17882260
  title: Coa1 links the Mss51 post-translational function to Cox1 cofactor insertion in cytochrome c oxidase assembly.
  findings:
  - statement: Coa1 and Shy1 participate in the Cox1 maturation/cofactor insertion step of complex IV assembly.
    supporting_text: "Shy1 has been implicated in formation of the heme a3-Cu(B) site in Cox1."
- id: PMID:24769239
  title: Quantitative variations of the mitochondrial proteome and phosphoproteome during fermentative and respiratory growth in Saccharomyces cerevisiae.
  findings: []
- id: PMID:35563734
  title: Pls1 Is a Peroxisomal Matrix Protein with a Role in Regulating Lysine Biosynthesis.
  findings: []
- id: PMID:9162072
  title: SHY1, the yeast homolog of the mammalian SURF-1 gene, encodes a mitochondrial protein required for respiration.
  findings:
  - statement: SHY1 encodes the yeast SURF1 homolog and localizes to the inner mitochondrial membrane.
    supporting_text: "The encoded protein is homologous to the product of the mammalian SURF-1 gene."
- id: file:yeast/SHY1/SHY1-deep-research-falcon.md
  title: Falcon deep research report on SHY1
  findings:
  - statement: Falcon synthesis identifies SHY1 as a SURF1-family inner mitochondrial membrane complex IV assembly factor.
core_functions:
- description: >-
    Shy1 is a SURF1-family mitochondrial inner membrane assembly factor for
    cytochrome c oxidase. It acts during Cox1 maturation and assembly
    intermediate progression, linking Mss51/Cox14-dependent Cox1 translational
    regulation to complex IV assembly and supercomplex formation.
  directly_involved_in:
  - id: GO:0033617
    label: mitochondrial respiratory chain complex IV assembly
  locations:
  - id: GO:0005743
    label: mitochondrial inner membrane
  supported_by:
  - reference_id: PMID:17882259
    supporting_text: "We suggest that Shy1 links Cox1 translational regulation to complex IV assembly and supercomplex formation."
  - reference_id: file:yeast/SHY1/SHY1-deep-research-falcon.md
    supporting_text: Falcon deep research emphasizes Cox1 maturation and complex IV assembly as the core SHY1 function.
proposed_new_terms: []
suggested_questions:
- question: >-
    Is there enough direct evidence to annotate a specific Shy1 molecular
    function for Cox1 cofactor insertion or assembly-intermediate stabilization,
    rather than leaving SHY1 represented only by the biological-process term for
    complex IV assembly?
  experts:
  - Mick DU
  - Rehling P
  - Winge DR
suggested_experiments:
- hypothesis: >-
    Shy1 promotes Cox1 heme a3:CuB maturation or maintains Cox1 in an
    assembly-competent state rather than binding unfolded proteins generally.
  description: >-
    Reconstitute Shy1-containing Cox1 assembly intermediates with Cox14, Mss51,
    Coa1 and cofactor-insertion factors, then test Shy1 mutants for Cox1
    cofactor incorporation, assembly-intermediate stability, and release of Mss51.
  experiment_type: mitochondrial complex IV assembly intermediate assay