Manganese-dependent superoxide dismutase localized to the mitochondrial matrix. SOD2 catalyzes the dismutation of superoxide radicals (O2•−) to hydrogen peroxide and molecular oxygen, serving as a critical antioxidant defense mechanism against reactive oxygen species generated during mitochondrial respiration. The enzyme contains one manganese ion per subunit and functions as a homotetramer.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005739 mitochondrion | IBA GO_REF:0000033 | ACCEPT | Summary: IBA annotation for mitochondrial localization based on phylogenetic inference across orthologous SOD2 proteins. Well-supported by multiple direct experimental observations confirming mitochondrial matrix localization. Reason: SOD2 is a well-established mitochondrial protein. The mitochondrial localization is supported by extensive evidence including direct biochemical purification from mitochondria, subcellular fractionation studies, and the presence of a mitochondrial transit peptide (residues 1-26) that is cleaved upon import. IBA inference from orthologous sequences is appropriate for this annotation as SOD2 localization is conserved across eukaryotes. Supporting Evidence: PMID:238997 The cyanide-insensitive superoxide dismutase of yeast has been shown to be localized in the mitochondrial matrix. PMID:15851472 Manganese-dependent superoxide dismutase 2 (SOD2) in the mitochondria plays a key role in protection against oxidative stress. |
| GO:0004784 superoxide dismutase activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA annotation for superoxide dismutase catalytic activity, inferred from orthologous SOD2 proteins. Core molecular function of SOD2 and highly conserved across eukaryotes. This annotation is more specific and appropriate than broader "oxidoreductase activity" annotations. The crystal structures of yeast SOD2 (PDB 3BFR, native Mn; PDB 3RN4, Fe-substituted; PMID:22102021) resolve the trigonal-bipyramidal active-site metal that catalyzes superoxide dismutation, directly supporting this molecular function. Reason: SOD2's primary molecular function is superoxide dismutase activity. The enzyme catalyzes conversion of superoxide anion to hydrogen peroxide and oxygen (EC 1.15.1.1). This is a highly specific and informative functional annotation representing the core catalytic activity. IBA inference is appropriate given the high conservation of this enzyme family across eukaryotes and consistent functional characterization of SOD2 orthologs. Supporting Evidence: PMID:238997 This enzyme has been isolated in good yield from bakers' yeast...This enzyme has activity comparable to that of other previously reported superoxide dismutases PMID:15851472 Manganese-dependent superoxide dismutase 2 (SOD2) in the mitochondria plays a key role in protection against oxidative stress file:yeast/SOD2/SOD2-deep-research-falcon.md Falcon literature synthesis supports SOD2 as the mitochondrial manganese superoxide dismutase that detoxifies superoxide generated during respiration. file:interpro/panther/PTHR11404/PTHR11404-metadata.yaml PANTHER PTHR11404 identifies SOD2 in the iron/manganese superoxide dismutase family. PMID:22102021 an enzyme which can convert superoxide radicals into the less toxic H 2 O 2 and O 2 |
| GO:0030145 manganese ion binding | IBA GO_REF:0000033 | ACCEPT | Summary: IBA annotation for manganese ion binding cofactor requirement. SOD2 requires manganese for catalytic activity with 1 Mn2+ per subunit. Critical for enzyme function and essential for distinguishing from cytoplasmic Fe-SOD1. The crystal structure of native SOD2 (PDB 3BFR; PMID:22102021) resolves the manganese ion at the active site, coordinated with distorted trigonal-bipyramidal geometry by three histidines, one aspartate and a solvent molecule; the companion Fe-substituted structure (PDB 3RN4) shows that iron misincorporation inactivates the enzyme, underscoring the manganese specificity of this binding site. Reason: SOD2 is a manganese-dependent superoxide dismutase, distinguishing it from the iron-dependent SOD1 isoform found in the cytoplasm. The UniProt entry explicitly states "Binds 1 Mn(2+) ion per subunit" with specific binding residues identified (positions 52, 107, 194, 198). Manganese insertion is essential during import into mitochondria and is mechanistically coupled to the mitochondrial import process. This annotation is more specific and informative than generic "metal ion binding" annotations and reflects the specialized cofactor requirement. Supporting Evidence: PMID:238997 This enzyme contains 1 atom of manganese per subunit and its absorption in the visible suggests Mn(III) in the resting enzyme. PMID:15851472 We found that a mitochondrial localization is essential...Manganese insertion is only possible with a newly synthesized polypeptide. PMID:22102021 The manganese or iron is invariably coordinated with distorted trigonal bipyramidal geometry by three histidines, one aspartate and a solvent molecule PMID:22102021 a high iron concentration in the mitochondria results in iron misincorporation at the active site, with subsequent inactivation of SOD2 |
| GO:0004784 superoxide dismutase activity | IEA GO_REF:0000120 | ACCEPT | Summary: IEA annotation via InterPro mapping (IPR001189: Mn/Fe superoxide dismutase). Redundant with IBA and IDA annotations for the same function but from automated computational mapping. Acceptable but less evidence-rich than experimental data. Reason: This IEA annotation derives from InterPro domain mapping, which appropriately identifies SOD2 as a superoxide dismutase based on conserved protein domains. While less informative than direct experimental evidence, automated annotations based on InterPro are generally reliable for well-characterized enzyme families. The annotation is not contradicted by experimental evidence and supports the core function identified by IBA and IDA annotations. Supporting Evidence: GO_REF:0000120 Combined Automated Annotation using Multiple IEA Methods based on InterPro domain mapping |
| GO:0005739 mitochondrion | IEA GO_REF:0000117 | ACCEPT | Summary: IEA annotation for mitochondrial localization via ARBA machine learning models. Represents automated inference from amino acid sequence patterns associated with mitochondrial proteins. Redundant with direct experimental evidence. Reason: ARBA machine learning models provide evidence for mitochondrial localization based on sequence patterns trained on experimentally validated mitochondrial proteins. While less directly informative than experimental evidence, this IEA annotation is consistent with and supported by extensive experimental data including direct biochemical purification and subcellular localization studies. |
| GO:0005759 mitochondrial matrix | IEA GO_REF:0000044 | ACCEPT | Summary: IEA annotation based on UniProtKB subcellular location vocabulary mapping to "Mitochondrion matrix". More specific than broader "mitochondrion" annotation, reflecting SOD2's precise subcellular compartment. Reason: The annotation correctly identifies the mitochondrial matrix as SOD2's specific subcellular compartment. This IEA is derived from structured UniProtKB annotation and is supported by direct experimental evidence. The matrix localization is essential for SOD2 function in protecting mitochondrial proteins and DNA from superoxide generated by the electron transport chain. This is more specific and informative than the broader "mitochondrion" annotations. Supporting Evidence: PMID:238997 The cyanide-insensitive superoxide dismutase of yeast has been shown to be localized in the mitochondrial matrix. |
| GO:0006801 superoxide metabolic process | IEA GO_REF:0000002 | ACCEPT | Summary: IEA annotation for involvement in superoxide metabolic process based on InterPro domain mapping. Reasonable but somewhat redundant with more specific process annotations like "removal of superoxide radicals". Reason: This annotation appropriately captures SOD2's involvement in superoxide metabolism through the dismutation reaction. However, it is broader than the more specific functional process "removal of superoxide radicals" (GO:0019430) which more precisely describes the biological outcome. The annotation is not incorrect but represents a higher-level categorization of the more specific process. |
| GO:0016209 antioxidant activity | IEA GO_REF:0000043 | ACCEPT | Summary: IEA annotation based on UniProtKB keyword mapping (KW-0049: Antioxidant). Accurate but relatively broad characterization of SOD2's functional role. Reason: SOD2 is correctly characterized as having antioxidant activity through its superoxide dismutase function. While this annotation is less specific than GO:0004784 (superoxide dismutase activity), it is accurate and captures the physiological consequence of the enzyme's catalytic activity. Antioxidant activity represents an appropriate functional categorization for SOD2. |
| GO:0016491 oxidoreductase activity | IEA GO_REF:0000043 | KEEP AS NON CORE | Summary: IEA annotation based on UniProtKB keyword mapping (KW-0560: Oxidoreductase). Correct but very broad categorization of enzymatic function. Reason: While technically correct that superoxide dismutase is an oxidoreductase enzyme (catalyzing electron transfer in the dismutation reaction), this annotation is overly broad and lacks specificity. The broader "oxidoreductase activity" encompasses thousands of diverse enzymatic activities and provides minimal functional information. More specific annotations like "superoxide dismutase activity" and "antioxidant activity" are far more informative. However, it is not incorrect, so retaining it as non-core is appropriate to avoid cluttering the functional annotation space. |
| GO:0019430 removal of superoxide radicals | IEA GO_REF:0000108 | ACCEPT | Summary: IEA annotation inferred via logical inference from the primary superoxide dismutase activity annotation. Accurately captures the functional consequence of SOD2's enzymatic activity. Reason: This process annotation appropriately captures the biological function of SOD2. The enzyme removes/detoxifies superoxide radicals by catalyzing their conversion to hydrogen peroxide and oxygen. This is the functional outcome of the superoxide dismutase catalytic activity and is logically inferred from that core function. The annotation is supported by extensive evidence of SOD2's role in cellular antioxidant defense. Supporting Evidence: PMID:3520557 MnSOD contributes to the natural protection of cells against oxygen toxicity PMID:22102021 a protein that resides in the mitochondrion and protects it against attack by superoxide radicals |
| GO:0046872 metal ion binding | IEA GO_REF:0000120 | KEEP AS NON CORE | Summary: IEA annotation for general metal ion binding based on InterPro domain mapping. Accurate but very broad and less specific than the manganese-specific annotation. Reason: SOD2 does bind a metal ion (specifically manganese), making this annotation technically correct. However, it is overly general and lacks the specificity that makes GO:0030145 (manganese ion binding) superior. While some genes may require annotation at this level of generality, SOD2's cofactor requirement is specifically and characteristically for manganese rather than other metal ions. The more specific "manganese ion binding" annotation is far more informative and should be prioritized. Retaining this as non-core avoids redundancy. |
| GO:0098869 cellular oxidant detoxification | IEA GO_REF:0000108 | ACCEPT | Summary: IEA annotation for cellular oxidant detoxification, inferred from antioxidant activity via logical inference. Captures the cellular process consequence of SOD2's enzymatic function. Reason: This process annotation appropriately characterizes SOD2's role in protecting cells from reactive oxygen species. The enzyme detoxifies superoxide and contributes to overall cellular antioxidant defense. The annotation is logically inferred from the antioxidant activity function and is supported by experimental evidence of SOD2's essential role in protecting cells against oxidative stress, particularly in mitochondria where high ROS levels are generated. |
| GO:0005739 mitochondrion | HDA PMID:24769239 Quantitative variations of the mitochondrial proteome and ph... | ACCEPT | Summary: HDA annotation from quantitative proteomic study identifying SOD2 in isolated mitochondria during proteomic survey of mitochondrial proteins under different growth conditions. Supports mitochondrial localization. Reason: This HDA annotation is based on direct detection of SOD2 protein in isolated mitochondrial fractions using mass spectrometry. Quantitative proteomics provides strong evidence for protein localization. The study systematically identified mitochondrial proteins and their relative abundance across different metabolic conditions. This represents solid experimental evidence for mitochondrial presence, though less specific than subcellular fractionation at the matrix level. Supporting Evidence: PMID:24769239 Label free quantitative analysis of protein accumulation revealed significant variation of 176 mitochondrial proteins |
| GO:0005739 mitochondrion | HDA PMID:11914276 Subcellular localization of the yeast proteome. | ACCEPT | Summary: HDA annotation from proteome-scale high-throughput subcellular localization study mapping yeast protein localization. Confirms mitochondrial localization through immunolocalization-based approach. Reason: This study represents the first large-scale proteome localization study in yeast, using high-throughput immunolocalization of epitope-tagged proteins to determine subcellular localization. SOD2 was identified among proteins localized to mitochondria in the GOA HDA record. The locally cached publication text contains the study abstract and methodology but not the SOD2-specific table entry, so this review cites the PMID-level method and treats matrix-specific localization as requiring additional evidence. Supporting Evidence: PMID:11914276 By high-throughput immunolocalization of tagged gene products, we have determined the subcellular localization of 2744 yeast proteins. |
| GO:0005739 mitochondrion | HDA PMID:14576278 The proteome of Saccharomyces cerevisiae mitochondria. | ACCEPT | Summary: HDA annotation from comprehensive mass spectrometry-based proteomics of purified yeast mitochondria. SOD2 identified in mitochondrial proteome catalog. Reason: This landmark study identified >750 different proteins from highly purified yeast mitochondria using tandem mass spectrometry. SOD2 was identified in this comprehensive mitochondrial proteome. The study analyzed only mitochondrial fractions, providing direct evidence for mitochondrial localization. This represents strong experimental support from a well-cited mitochondrial proteomics resource. Supporting Evidence: PMID:14576278 From >20 million MS spectra, 750 different proteins were identified, indicating an involvement of mitochondria in numerous cellular processes |
| GO:0005739 mitochondrion | HDA PMID:16823961 Toward the complete yeast mitochondrial proteome: multidimen... | ACCEPT | Summary: HDA annotation from advanced proteomics study combining multidimensional separation techniques to characterize the complete yeast mitochondrial proteome. Reason: This study used orthogonal proteomics approaches to achieve the most comprehensive characterization of the yeast mitochondrial proteome, identifying 851 different proteins. SOD2 was identified as a mitochondrial protein in this resource. The use of multiple complementary separation and detection methods increases confidence in protein identification. This represents high-quality experimental evidence for mitochondrial localization from a mature proteomics platform. Supporting Evidence: PMID:16823961 A total of 851 different proteins (PROMITO dataset) were identified by use of multidimensional LC-MS/MS |
| GO:0004784 superoxide dismutase activity | IDA PMID:15851472 Manganese activation of superoxide dismutase 2 in the mitoch... | ACCEPT | Summary: IDA annotation from direct enzymatic assay study characterizing manganese activation of SOD2 in mitochondria. Demonstrates enzyme activity and essential cofactor requirement. Reason: This IDA annotation is from direct biochemical characterization of SOD2 enzyme activity in mitochondrial context. The study specifically examined manganese activation of SOD2, demonstrating the enzyme's superoxide dismutase activity and its dependence on mitochondrial import for proper cofactor insertion. This represents strong experimental evidence for the core molecular function. Supporting Evidence: PMID:15851472 Manganese-dependent superoxide dismutase 2 (SOD2) in the mitochondria plays a key role in protection against oxidative stress. Here we probed the pathway by which SOD2 acquires its manganese catalytic cofactor. |
| GO:0004784 superoxide dismutase activity | IDA PMID:238997 Isolation and characterization of a manganese-containing sup... | ACCEPT | Summary: IDA annotation from the landmark 1975 study that first isolated and characterized manganese-containing SOD from yeast. Original biochemical characterization of enzyme activity. Reason: This is from the seminal study that first isolated yeast mitochondrial SOD and demonstrated its superoxide dismutase activity in vitro. The study characterized the enzyme's molecular weight (96,000 Da tetramer), subunit structure, manganese content (1 Mn per subunit), and catalytic activity. This represents foundational experimental evidence for SOD2's molecular function and remains a critical reference for the enzyme's properties. Supporting Evidence: PMID:238997 This enzyme has been isolated in good yield from bakers' yeast...This enzyme contains 1 atom of manganese per subunit...This enzyme has activity comparable to that of other previously reported superoxide dismutases |
| GO:0005739 mitochondrion | IDA PMID:15851472 Manganese activation of superoxide dismutase 2 in the mitoch... | ACCEPT | Summary: IDA annotation from manganese activation study that demonstrated SOD2's mitochondrial localization is essential for cofactor insertion and activation. Reason: The study directly showed that mitochondrial localization of SOD2 is essential for proper manganese insertion and enzyme activation. Cytosolic versions of SOD2 remain largely apo (without manganese) unless cells are exposed to toxic manganese levels. This demonstrates mechanistically that SOD2's mitochondrial localization is not just coincidental but essential for function. The study provides strong experimental evidence for mitochondrial localization integrated with functional characterization. Supporting Evidence: PMID:15851472 We found that a mitochondrial localization is essential...By reversibly blocking mitochondrial import in vivo, we noted that newly synthesized Sod2p can enter mitochondria but not a Sod2p polypeptide that was allowed to accumulate in the cytosol. |
| GO:0005759 mitochondrial matrix | IDA PMID:238997 Isolation and characterization of a manganese-containing sup... | ACCEPT | Summary: IDA annotation from original characterization study that specifically localized the enzyme to the mitochondrial matrix compartment. Foundational evidence for subcellular compartmentalization. Reason: The seminal 1975 study explicitly localized the cyanide-insensitive (manganese) superoxide dismutase to the mitochondrial matrix, the innermost mitochondrial compartment where the electron transport chain generates superoxide and where SOD2 provides essential antioxidant protection. This specific subcellular localization is more informative than broader mitochondrion annotations and accurately reflects the enzyme's functional compartment. This remains the gold standard evidence for matrix localization. Supporting Evidence: PMID:238997 The cyanide-insensitive superoxide dismutase of yeast has been shown to be localized in the mitochondrial matrix. |
| GO:0072593 reactive oxygen species metabolic process | IMP PMID:3520557 A yeast mutant lacking mitochondrial manganese-superoxide di... | ACCEPT | Summary: IMP annotation from genetic knockout study demonstrating that SOD2 is essential for cellular protection against oxygen-induced ROS toxicity. Establishes biological role in ROS metabolism. Reason: This IMP annotation is from a landmark genetic study that created a SOD2-null mutant and demonstrated its hypersensitivity to oxygen. The mutant lacked cyanide-insensitive SOD activity and exhibited growth inhibition in oxygen-containing atmospheres, providing direct genetic evidence that SOD2 contributes to cellular defense against oxygen toxicity through ROS metabolism. This represents the strongest type of biological process evidence showing that loss of protein function impairs the process. Supporting Evidence: PMID:3520557 In the absence of oxygen, the mutant grew as rapidly as the wild-type parent. However, increasing concentrations of oxygen led to a progressive inhibition of growth. The properties of this mutant provide direct evidence that MnSOD contributes to the natural protection of cells against oxygen toxicity. |
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Download this section (compressed HTML)Q: What role does SOD2 phosphorylation play in regulating its activity or localization?
Q: Are there condition-specific changes in SOD2 expression or activity in response to metabolic state?
Q: Does SOD2 interact with other mitochondrial proteins to form a larger antioxidant defense complex?
Experiment: Detailed kinetic analysis of SOD2 with various superoxide concentrations and pH conditions to establish optimal activity parameters in vivo
Experiment: Investigation of SOD2 regulation by reactive oxygen species or other cellular signals that might modulate its expression
Experiment: Analysis of the relationship between SOD2 activity and cellular aging or replicative lifespan in yeast
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