Mouse Surf1 encodes surfeit locus protein 1, a conserved nuclear-encoded mitochondrial inner membrane protein in the SURF1/Shy1 family. It is a cytochrome c oxidase (mitochondrial respiratory chain complex IV) assembly factor rather than a catalytic complex IV subunit, and has no cytochrome-c oxidase or proton-transport activity of its own. UniProt describes mouse SURF1 as a component of the MITRAC mitochondrial translation regulation assembly intermediate, and mouse knockout studies show isolated complex IV deficiency with elevated lactate and motor phenotypes. SURF1 acts at early/intermediate COX biogenesis, probably stabilizing COX1-module assembly and/or supporting heme a3-CuB catalytic-center maturation.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0033617 mitochondrial respiratory chain complex IV assembly | IBA GO_REF:0000033 | ACCEPT | Summary: Accept. This is the central conserved role of Surf1. The IBA is supported by the SURF1/Shy1 family node and by characterized orthologs including human SURF1 and yeast Shy1. Mouse evidence is concordant: Surf1 knockout causes isolated cytochrome c oxidase deficiency, while UniProt describes SURF1 as a MITRAC component that regulates COX assembly. Reason: GO:0033617 captures the core biological process without assigning SURF1 catalytic activity. PANTHER/family context is appropriate here because it is the explicit basis of this IBA annotation and agrees with mouse experimental and UniProt evidence. Supporting Evidence: UniProt:P09925 Component of the MITRAC complex. Regulates cytochrome c oxidase assembly. PMID:12566387 We report here the creation of a constitutive knockout mouse for SURF1, a gene encoding one of the assembly proteins involved in the formation of cytochrome c oxidase (COX). file:mouse/Surf1/Surf1-deep-research-falcon.md The requested target corresponds to the mammalian SURF1-family protein that functions as a mitochondrial cytochrome c oxidase assembly factor. |
| GO:0005739 mitochondrion | IBA GO_REF:0000033 | ACCEPT | Summary: Accept. Surf1 acts in mitochondria, specifically at the mitochondrial inner membrane. The IBA mitochondrion term is broad but correct for the active site of the assembly-factor function. Reason: Mitochondrial localization is strongly supported by UniProt, mitochondrial proteomics, and the conserved SURF1/Shy1 family context. More precise inner membrane localization is represented in the core function and in replacement suggestions for broader membrane terms. Supporting Evidence: UniProt:P09925 SUBCELLULAR LOCATION: Mitochondrion membrane; Multi-pass membrane protein. file:mouse/Surf1/Surf1-deep-research-falcon.md Surf1 is described as synthesized as a larger precursor with an N-terminal leader peptide that is cleaved, and the mature protein is embedded in the mitochondrial inner membrane where it participates in COX assembly. |
| GO:1902600 proton transmembrane transport | IEA GO_REF:0000108 | REMOVE | Summary: Remove. This electronic annotation is a logical consequence of the cytochrome-c oxidase activity annotation. It incorrectly propagates the proton-pumping process of assembled complex IV to SURF1, which is an assembly factor and not the proton-translocating enzyme. Reason: SURF1 loss affects proton-pumping capacity indirectly by impairing complex IV assembly. The gene product itself is not a transporter or a catalytic COX subunit, so GO:1902600 is an over-annotation. Supporting Evidence: UniProt:P09925 Regulates cytochrome c oxidase assembly. file:mouse/Surf1/Surf1-deep-research-falcon.md SURF1 is not an enzyme catalyzing a chemical transformation; its primary biochemical role is as an inner-membrane assembly factor/chaperone-like protein that promotes correct maturation and/or progression of COX assembly intermediates. |
| GO:0016020 membrane | IEA GO_REF:0000002 | MODIFY | Summary: Modify. The InterPro-derived membrane annotation is directionally correct because SURF1 is a multi-pass membrane protein, but it is too general for a reviewed gene record. The supported location is mitochondrial inner membrane. Reason: SURF1 contains predicted transmembrane helices and functions at the mitochondrial inner membrane as part of COX assembly machinery. Replacing the generic membrane term with GO:0005743 is more informative and consistent with the curated evidence. Proposed replacements: mitochondrial inner membrane Supporting Evidence: UniProt:P09925 SUBCELLULAR LOCATION: Mitochondrion membrane; Multi-pass membrane protein. TRANSMEM 68..86 and 280..300. file:mouse/Surf1/Surf1-deep-research-falcon.md Surf1 is embedded in the mitochondrial inner membrane where it participates in COX assembly. |
| GO:0031966 mitochondrial membrane | IEA GO_REF:0000044 | MODIFY | Summary: Modify. Mitochondrial membrane localization is correct but still less precise than the supported mitochondrial inner membrane location for a multi-pass COX assembly factor. Reason: UniProt and Falcon both support mitochondrial membrane localization, and the mechanistic evidence places SURF1 in the inner membrane COX assembly machinery. GO:0005743 is the better curated cellular component term. Proposed replacements: mitochondrial inner membrane Supporting Evidence: UniProt:P09925 SUBCELLULAR LOCATION: Mitochondrion membrane; Multi-pass membrane protein. file:mouse/Surf1/Surf1-deep-research-falcon.md Mouse Surf1 is described as a small inner mitochondrial membrane protein synthesized with an N-terminal targeting presequence and inserted into the IMM. |
| GO:0033617 mitochondrial respiratory chain complex IV assembly | ISO GO_REF:0000119 | ACCEPT | Summary: Accept. Orthology transfer from human SURF1 is appropriate because the mouse and human proteins have the same conserved COX assembly-factor role, and mouse loss-of-function studies independently support complex IV deficiency. Reason: The transferred process term matches the mouse experimental phenotype and the UniProt functional statement. It does not overstate SURF1 as a catalytic COX subunit. Supporting Evidence: UniProt:P09925 Regulates cytochrome c oxidase assembly. PMID:12566387 These results indicate a function for murine Surf1 protein specifically related to COX and recapitulate, at least in part, the human phenotype. |
| GO:0033617 mitochondrial respiratory chain complex IV assembly | IEA GO_REF:0000107 | ACCEPT | Summary: Accept. The Ensembl Compara transfer from human SURF1 to mouse Surf1 is appropriate for the conserved assembly process. Reason: GO:0033617 is the best existing GO process term for Surf1. The automatic transfer is supported by mouse knockout evidence and UniProt's curated MITRAC/COX assembly statement. Supporting Evidence: UniProt:P09925 Component of the MITRAC complex. Regulates cytochrome c oxidase assembly. file:mouse/Surf1/Surf1-deep-research-falcon.md Multiple lines of evidence indicate that SURF1 deficiency causes accumulation of early COX intermediates and reduced mature COX holoenzyme. |
| GO:0004129 cytochrome-c oxidase activity | IMP PMID:23838831 Decreased in vitro mitochondrial function is associated with... | MODIFY | Summary: Modify. PMID:23838831 shows reduced complex IV activity in Surf1-deficient mouse brain mitochondria, but that phenotype does not mean SURF1 itself enables cytochrome-c oxidase activity. SURF1 is an assembly factor whose loss reduces the amount or quality of assembled COX. Reason: GO:0004129 is the catalytic activity of the complex IV holoenzyme. SURF1 is not a catalytic or structural COX subunit. The experimental phenotype supports involvement in mitochondrial respiratory chain complex IV assembly, not direct oxidase activity. Proposed replacements: mitochondrial respiratory chain complex IV assembly Supporting Evidence: PMID:23838831 ATP production in brain mitochondria isolated from Surf1 KO mice remained unchanged despite a 49% reduction in COX activity, a 24% reduction in state 3 respiration, and a 24% increase in H 2 O 2 production. UniProt:P09925 Regulates cytochrome c oxidase assembly. |
| GO:0033617 mitochondrial respiratory chain complex IV assembly | ISS GO_REF:0000024 | ACCEPT | Summary: Accept. Sequence-similarity transfer from human SURF1 is consistent with the conserved SURF1/Shy1 family role and with direct mouse knockout evidence for isolated COX deficiency. Reason: The term is specific, correctly in the biological-process branch, and matches the synthesis from UniProt, mouse publications, and Falcon. Supporting Evidence: UniProt:P09925 Component of the MITRAC complex. Regulates cytochrome c oxidase assembly. file:mouse/Surf1/Surf1-deep-research-falcon.md Authoritative reviews and primary biochemical work converge on SURF1 as an early/intermediate complex IV assembly factor. |
| GO:0005739 mitochondrion | HDA PMID:18614015 A mitochondrial protein compendium elucidates complex I dise... | ACCEPT | Summary: Accept. MitoCarta/high-throughput proteomics support mitochondrial localization. This term is broad but correct. Reason: PMID:18614015 created a mitochondrial compendium using mass spectrometry, GFP tagging, and machine learning across mouse tissues. Together with UniProt's membrane localization, this supports retaining the mitochondrion CC annotation. Supporting Evidence: PMID:18614015 We performed mass spectrometry, GFP tagging, and machine learning to create a mitochondrial compendium of 1098 genes and their protein expression across 14 mouse tissues. UniProt:P09925 SUBCELLULAR LOCATION: Mitochondrion membrane. |
| GO:0005739 mitochondrion | HDA PMID:14651853 Integrated analysis of protein composition, tissue diversity... | ACCEPT | Summary: Accept. The MGI HDA annotation is supported by a mouse mitochondrial proteomic survey. The GOA file contains repeated identical HDA rows for this PMID; this review represents that repeated mitochondrion annotation. Reason: PMID:14651853 supports broad mitochondrial localization. It does not by itself establish inner membrane topology, but it is concordant with the more specific UniProt and Falcon evidence. Supporting Evidence: PMID:14651853 We performed a proteomic survey of mitochondria from mouse brain, heart, kidney, and liver and combined the results with existing gene annotations to produce a list of 591 mitochondrial proteins. UniProt:P09925 SUBCELLULAR LOCATION: Mitochondrion membrane. |
| GO:0004129 cytochrome-c oxidase activity | IMP PMID:12566387 Constitutive knockout of Surf1 is associated with high embry... | MODIFY | Summary: Modify. The cited mouse knockout paper shows a profound isolated defect of COX activity after Surf1 loss and explicitly describes Surf1 as an assembly protein involved in COX formation. The phenotype supports COX assembly, not direct oxidase activity by SURF1. Reason: GO:0004129 should be annotated to the cytochrome c oxidase complex or its catalytic subunits, not to a transient assembly factor. The correct interpretation of the IMP evidence is that SURF1 is required for mitochondrial respiratory chain complex IV assembly. Proposed replacements: mitochondrial respiratory chain complex IV assembly Supporting Evidence: PMID:12566387 The murine phenotype is characterized by a profound and isolated defect of COX activity in skeletal muscle and liver, and, to a lesser extent, heart and brain. PMID:12566387 We report here the creation of a constitutive knockout mouse for SURF1, a gene encoding one of the assembly proteins involved in the formation of cytochrome c oxidase (COX). |
| GO:0062011 mitochondrial respiratory chain complex IV pre-assembly complex | IEA | NEW | Summary: Proposed new annotation. UniProt states that mouse SURF1 is a component of MITRAC, and Falcon synthesis identifies MITRAC as the assembly intermediate where SURF1 acts during COX1-module maturation. This CC term is more informative than a generic protein-binding annotation and captures the assembly complex rather than the mature respiratory chain complex. Reason: GO:0062011 describes the mitochondrial respiratory chain complex IV pre-assembly complex, which corresponds to MITRAC. The evidence is partly by similarity to human SURF1 and homolog studies, so this should be used as a conservative proposed CC annotation rather than as proof of a new mouse-specific molecular activity. Supporting Evidence: UniProt:P09925 SUBUNIT: Component of the MITRAC complex, the core components of this complex being COA3/MITRAC12 and COX14. Interacts with COA3. file:mouse/Surf1/Surf1-deep-research-falcon.md SURF1 functions within the MITRAC complex, a specialized assembly machinery that couples COX1 synthesis with early assembly steps. |
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Download this section (compressed HTML)Q: For mouse Surf1 specifically, can the MITRAC/pre-assembly-complex placement be demonstrated directly rather than inferred from human SURF1 and homolog systems?
Q: Does mouse SURF1 directly influence heme a3-CuB center maturation, or is that mechanistic detail primarily a conserved-family inference from bacterial and yeast homolog studies?
Q: What tissue-specific compensatory mechanisms explain the milder mouse phenotype despite substantial complex IV deficiency?
Experiment: Perform endogenous tagging or immunoprecipitation of mouse SURF1 followed by native complex analysis and mass spectrometry to test direct membership in MITRAC/GO:0062011 in mouse tissues or cells.
Type: proteomics
Experiment: Use pulse-labeling, blue-native PAGE, and complex IV assembly-intermediate profiling in Surf1 knockout and rescued mouse cells to map the blocked assembly step.
Type: respiratory-chain assembly assay
Experiment: Measure COX1 heme a/heme a3 and copper-center maturation in Surf1-deficient mouse mitochondria to test whether the heme a3-CuB mechanism inferred from homolog systems applies directly to mouse SURF1.
Type: biochemical cofactor assay
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