LONP1 is the nuclear-encoded mitochondrial Lon protease, synthesized as a precursor and processed after import into the mitochondrial matrix. The canonical protein assembles into a homo-oligomeric ring-shaped AAA+ machine whose ATPase cycle recognizes, unfolds, and translocates selected misfolded, unassembled, oxidatively damaged, or short-lived proteins into a serine protease chamber for degradation. LONP1 also has a separable, protease-independent ATP-dependent chaperone activity that assists folding and suppresses aggregation of newly imported matrix and inner-membrane proteins, thereby supporting mitochondrial proteostasis and organization. Binding to single-stranded mitochondrial DNA and RNA is a genuine secondary property, but its physiological regulatory consequences remain incompletely defined. Isoforms 2 and 3 delete N-terminal sequence that overlaps or removes the canonical targeting region, so their mitochondrial localization and ability to execute the matrix protease and chaperone functions are not established.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004176 ATP-dependent peptidase activity | IBA GO_REF:0000033 | ACCEPT | Summary: Conserved core activity of the mitochondrial Lon AAA+ protease. Reason: Human LONP1 directly couples ATP utilization to proteolysis, and the phylogenetic inference agrees with multiple human biochemical studies (PMID:8248235; PMID:14739292; PMID:17420247). Propagation Review Root cause: NO FAILURE CORE Sources checked: MGI:MGI:1921392 SUPPORTS TRANSFER PANTHER:PTN001599760 SUPPORTS TRANSFER RGD:621598 SUPPORTS TRANSFER SGD:S000000118 SUPPORTS TRANSFER UniProtKB:P36776 SUPPORTS TRANSFER UniProtKB:P93655 SUPPORTS TRANSFER |
| GO:0006515 protein quality control for misfolded or incompletely synthesized proteins | IBA GO_REF:0000033 | ACCEPT | Summary: Core mitochondrial proteostasis role supported by substrate-selective degradation and loss-of-function evidence. Reason: LONP1 recognizes and degrades damaged or unstable mitochondrial proteins, including oxidized aconitase (PMID:12198491), so the IBA term is appropriately scoped. Propagation Review Root cause: NO FAILURE CORE Sources checked: FB:FBgn0036892 SUPPORTS TRANSFER PANTHER:PTN001599760 SUPPORTS TRANSFER SGD:S000000118 SUPPORTS TRANSFER UniProtKB:P93655 SUPPORTS TRANSFER |
| GO:0007005 mitochondrion organization | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: LONP1 is required to maintain normal mitochondrial structure and function as a downstream consequence of proteostasis. Reason: LONP1 depletion produces severe mitochondrial morphological and functional defects (PMID:15683722), independently validating the conserved inference, but this broad process is downstream of the defining matrix protease and chaperone activities. Propagation Review Root cause: NO FAILURE NON CORE Sources checked: FB:FBgn0036892 SUPPORTS TRANSFER PANTHER:PTN000005479 SUPPORTS TRANSFER PomBase:SPAC22F3.06c SUPPORTS TRANSFER RGD:621598 SUPPORTS TRANSFER UniProtKB:P36776 SUPPORTS TRANSFER |
| GO:0005759 mitochondrial matrix | IBA GO_REF:0000033 | ACCEPT | Summary: Correct active compartment for mature human LONP1. Reason: LONP1 is a nuclear-encoded precursor imported into the mitochondrial matrix, where its protease and chaperone activities operate (PMID:8248235; PMID:33431889). Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN000005479 SUPPORTS TRANSFER RGD:621598 SUPPORTS TRANSFER SGD:S000000118 SUPPORTS TRANSFER UniProtKB:P36776 SUPPORTS TRANSFER UniProtKB:Q59HJ6 SUPPORTS TRANSFER |
| GO:0003697 single-stranded DNA binding | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Conserved nucleic-acid-binding activity that is directly demonstrated for human LONP1 but has an unresolved physiological consequence. Reason: Human LONP1 binds single-stranded G-rich mitochondrial DNA in vitro and associates with mtDNA in cells (PMID:9485316; PMID:14739292; PMID:17420247), but this remains secondary to its protease/chaperone core. Propagation Review Root cause: NO FAILURE NON CORE Sources checked: MGI:MGI:1921392 SUPPORTS TRANSFER PANTHER:PTN000005479 SUPPORTS TRANSFER |
| GO:0004176 ATP-dependent peptidase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Correct automated assignment of the defining ATP-dependent protease activity. Reason: Domain/rule inference is independently confirmed by direct human biochemical evidence (PMID:8248235; PMID:14739292; PMID:17420247). Propagation Review Root cause: NO FAILURE CORE Sources checked: ARBA:ARBA00087186 SUPPORTS TRANSFER UniProtKB:Q8CGK3 SUPPORTS TRANSFER ensembl:ENSMUSP00000041814 SUPPORTS TRANSFER UniProtKB:Q924S5 SUPPORTS TRANSFER ensembl:ENSRNOP00000066618 SUPPORTS TRANSFER InterPro:IPR004815 SUPPORTS TRANSFER InterPro:IPR008268 SUPPORTS TRANSFER InterPro:IPR008269 SUPPORTS TRANSFER InterPro:IPR027065 SUPPORTS TRANSFER UniRule:UR000376739 SUPPORTS TRANSFER |
| GO:0004252 serine-type endopeptidase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Correct specific catalytic-class annotation for the Lon serine protease domain. Reason: Human LONP1 has the catalytic serine protease activity EC 3.4.21.53, supported by mutagenesis and proteolysis assays (PMID:14739292; PMID:17420247; PMID:24520911). Propagation Review Root cause: NO FAILURE CORE Sources checked: InterPro:IPR008268 SUPPORTS TRANSFER InterPro:IPR008269 SUPPORTS TRANSFER InterPro:IPR027065 SUPPORTS TRANSFER InterPro:IPR027503 SUPPORTS TRANSFER EC:3.4.21.53 SUPPORTS TRANSFER UniRule:UR000376739 SUPPORTS TRANSFER |
| GO:0005524 ATP binding | IEA GO_REF:0000120 | KEEP AS NON CORE | Summary: True but generic nucleotide-binding subactivity of the AAA+ ATPase. Reason: ATP binding is experimentally established (PMID:14739292), but ATP hydrolysis and ATP-dependent peptidase/chaperone activities are more informative descriptions of LONP1 function. Propagation Review Root cause: NO FAILURE NON CORE Failure modes: GRANULARITY MISMATCH Sources checked: InterPro:IPR003959 SUPPORTS TRANSFER InterPro:IPR004815 SUPPORTS TRANSFER InterPro:IPR027065 SUPPORTS TRANSFER UniRule:UR000376739 SUPPORTS TRANSFER |
| GO:0005759 mitochondrial matrix | IEA GO_REF:0000120 | ACCEPT | Summary: Correct matrix localization inferred from orthologs and targeting features. Reason: The automated call agrees with direct human localization and functional studies (PMID:8248235; PMID:33431889). Propagation Review Root cause: NO FAILURE CORE Sources checked: UniProtKB:Q924S5 SUPPORTS TRANSFER ensembl:ENSRNOP00000066618 SUPPORTS TRANSFER UniProtKB-SubCell:SL-0170 SUPPORTS TRANSFER UniRule:UR000376739 SUPPORTS TRANSFER |
| GO:0006508 proteolysis | IEA GO_REF:0000002 | MODIFY | Summary: Proteolysis is correct but unnecessarily broad for a mitochondrial matrix protease. Reason: Replace the generic parent process with mitochondrial protein catabolic process, which captures LONP1's experimentally established substrate degradation in the matrix (PMID:12198491; PMID:37327776). Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: GRANULARITY MISMATCH Sources checked: InterPro:IPR004815 SUPPORTS TRANSFER InterPro:IPR008268 SUPPORTS TRANSFER InterPro:IPR008269 SUPPORTS TRANSFER Proposed replacements: mitochondrial protein catabolic process |
| GO:0006515 protein quality control for misfolded or incompletely synthesized proteins | IEA GO_REF:0000120 | ACCEPT | Summary: Correct core proteostasis process inferred from the Lon protease family. Reason: Direct human evidence shows selective degradation of damaged proteins and ATPase-dependent assistance of folding (PMID:12198491; PMID:33431889). Propagation Review Root cause: NO FAILURE CORE Sources checked: InterPro:IPR027503 SUPPORTS TRANSFER UniRule:UR000376739 SUPPORTS TRANSFER |
| GO:0016887 ATP hydrolysis activity | IEA GO_REF:0000120 | ACCEPT | Summary: Defining AAA+ ATPase activity of LONP1. Reason: ATP hydrolysis drives degradation of intact protein substrates and the chaperone function of human LONP1 (PMID:24520911; PMID:33431889). Propagation Review Root cause: NO FAILURE CORE Sources checked: UniProtKB:Q8CGK3 SUPPORTS TRANSFER ensembl:ENSMUSP00000041814 SUPPORTS TRANSFER InterPro:IPR003959 SUPPORTS TRANSFER RHEA:13065 SUPPORTS TRANSFER UniRule:UR000376739 SUPPORTS TRANSFER |
| GO:0030163 protein catabolic process | IEA GO_REF:0000120 | MODIFY | Summary: Protein catabolism is correct but a more informative mitochondrial child term is available. Reason: LONP1 acts on mitochondrial proteins; GO:0035694 captures the experimentally supported compartment-specific process (PMID:12198491; PMID:37327776). Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: GRANULARITY MISMATCH Sources checked: UniProtKB:Q924S5 SUPPORTS TRANSFER ensembl:ENSRNOP00000066618 SUPPORTS TRANSFER InterPro:IPR027065 SUPPORTS TRANSFER Proposed replacements: mitochondrial protein catabolic process |
| GO:0034599 cellular response to oxidative stress | IEA GO_REF:0000104 | KEEP AS NON CORE | Summary: Defensible secondary process reflecting LONP1-dependent clearance of oxidized proteins. Reason: Human experiments show that LONP1 loss impairs clearance of oxidatively modified aconitase (PMID:12198491), but the broad cellular response term is less direct than oxidation-dependent protein catabolism. Propagation Review Root cause: NO FAILURE NON CORE Failure modes: GRANULARITY MISMATCH Sources checked: UniRule:UR000376739 SUPPORTS TRANSFER |
| GO:0043565 sequence-specific DNA binding | IEA GO_REF:0000104 | MODIFY | Summary: Sequence selectivity is supported, but the transferred term omits the decisive single-stranded substrate constraint. Reason: LONP1 preferentially binds G-rich single-stranded mitochondrial DNA sequences (PMID:9485316; PMID:14739292; PMID:17420247), so sequence-specific single-stranded DNA binding preserves both demonstrated properties. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: GRANULARITY MISMATCH Sources checked: UniRule:UR000376739 SUPPORTS TRANSFER Proposed replacements: sequence-specific single stranded DNA binding |
| GO:0051131 chaperone-mediated protein complex assembly | IEA GO_REF:0000104 | MODIFY | Summary: The transferred assembly process is too indirect and should be represented by LONP1's demonstrated folding activity. Reason: Human evidence establishes ATPase-dependent chaperone activity and cooperation with mtHSP70 in de novo folding (PMID:33431889), whereas generic chaperone-mediated complex assembly overstates the specific outcome. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: ROLE CONFLATION GRANULARITY MISMATCH Sources checked: UniRule:UR000376739 SUPPORTS SOURCE BUT NOT TARGET Proposed replacements: 'de novo' protein folding |
| GO:0070407 oxidation-dependent protein catabolic process | IEA GO_REF:0000104 | ACCEPT | Summary: Well-supported core process for selective turnover of oxidatively damaged matrix proteins. Reason: LONP1 selectively recognizes and degrades mildly oxidized aconitase in an ATP-stimulated manner (PMID:12198491). Propagation Review Root cause: NO FAILURE CORE Sources checked: UniRule:UR000376739 SUPPORTS TRANSFER |
| GO:0005515 protein binding | IPI PMID:24520911 Mutations to a glycine loop in the catalytic site of human L... | MARK AS OVER ANNOTATED | Summary: Uninformative substrate interaction recorded as generic protein binding. Reason: Beta-casein was used as a model protease substrate in biochemical assays (PMID:24520911). Its interaction demonstrates substrate engagement but does not define a distinct molecular function beyond ATP-dependent proteolysis. |
| GO:0005515 protein binding | IPI PMID:33961781 Dual proteome-scale networks reveal cell-specific remodeling... | MARK AS OVER ANNOTATED | Summary: Generic interaction-screen result without a defined LONP1 molecular function. Reason: The BioPlex proteome-scale affinity-purification study reports interaction networks (PMID:33961781), but GO:0005515 is uninformative and the row provides no demonstrated functional consequence. |
| GO:0005515 protein binding | IPI PMID:40205054 Multimodal cell maps as a foundation for structural and func... | MARK AS OVER ANNOTATED | Summary: Generic high-throughput interaction evidence that does not establish a distinct molecular activity. Reason: The multimodal cell-map study is large-scale interaction/resource evidence (PMID:40205054). Retaining generic protein binding as a function would overstate the biological interpretation of the association. |
| GO:0001666 response to hypoxia | IEA GO_REF:0000107 | KEEP AS NON CORE | Summary: Valid contextual response supported directly in human cells, but not a core constitutive role. Reason: Hypoxia induces LON expression through HIF-1 and LONP1 mediates COX4-1 degradation during the adaptive COX4 switch (PMID:17418790). Propagation Review Root cause: NO FAILURE NON CORE Failure modes: CONTEXT OR TISSUE MISMATCH Sources checked: UniProtKB:Q924S5 SUPPORTS TRANSFER ensembl:ENSRNOP00000066618 SUPPORTS TRANSFER |
| GO:0003697 single-stranded DNA binding | IEA GO_REF:0000107 | KEEP AS NON CORE | Summary: Correct orthology transfer independently supported by human biochemical data, but not a defining core activity. Reason: Human LONP1 binds single-stranded G-rich mitochondrial DNA (PMID:9485316; PMID:14739292; PMID:17420247), but the physiological regulatory consequence remains unresolved. Propagation Review Root cause: NO FAILURE NON CORE Sources checked: UniProtKB:Q8CGK3 SUPPORTS TRANSFER ensembl:ENSMUSP00000041814 SUPPORTS TRANSFER |
| GO:0005739 mitochondrion | IEA GO_REF:0000120 | KEEP AS NON CORE | Summary: Correct but less specific parent localization. Reason: Human LONP1 is mitochondrial, with stronger evidence specifically placing the active mature enzyme in the matrix (PMID:8248235; PMID:33431889). Propagation Review Root cause: NO FAILURE NON CORE Failure modes: GRANULARITY MISMATCH Sources checked: ARBA:ARBA00026962 SUPPORTS TRANSFER UniProtKB:Q8CGK3 SUPPORTS TRANSFER ensembl:ENSMUSP00000041814 SUPPORTS TRANSFER |
| GO:0007005 mitochondrion organization | IEA GO_REF:0000107 | KEEP AS NON CORE | Summary: Correct orthology transfer supported by a human knockdown phenotype, but broad and downstream. Reason: LONP1 downregulation causes abnormal mitochondrial morphology and function (PMID:15683722), but the organization phenotype is downstream of mitochondrial proteostasis rather than the defining molecular function. Propagation Review Root cause: NO FAILURE NON CORE Sources checked: UniProtKB:Q924S5 SUPPORTS TRANSFER ensembl:ENSRNOP00000066618 SUPPORTS TRANSFER |
| GO:0009725 response to hormone | IEA GO_REF:0000107 | MARK AS OVER ANNOTATED | Summary: Broad organismal-context transfer that is not a core LONP1 function. Reason: A response-to-hormone phenotype in a rodent ortholog is not sufficient to make this generic process a conserved human LONP1 function; human evidence instead defines mitochondrial protease and chaperone activities. Propagation Review Root cause: PROPAGATION BAD Failure modes: CONTEXT OR TISSUE MISMATCH Sources checked: UniProtKB:Q924S5 SUPPORTS SOURCE BUT NOT TARGET ensembl:ENSRNOP00000066618 SUPPORTS SOURCE BUT NOT TARGET |
| GO:0010044 response to aluminum ion | IEA GO_REF:0000107 | REMOVE | Summary: Exposure-specific rodent phenotype should not be propagated as a conserved human function. Reason: No human LONP1 evidence connects the mitochondrial Lon protease to an aluminum-ion response, and this environmental phenotype is not intrinsic to orthology. Propagation Review Root cause: PROPAGATION BAD Failure modes: CONTEXT OR TISSUE MISMATCH Sources checked: UniProtKB:Q924S5 SUPPORTS SOURCE BUT NOT TARGET ensembl:ENSRNOP00000066618 SUPPORTS SOURCE BUT NOT TARGET |
| GO:0042731 PH domain binding | IEA GO_REF:0000107 | REMOVE | Summary: Ortholog-transferred binding claim unsupported by human LONP1 biology. Reason: PH-domain binding is not part of the experimentally established human LONP1 protease, ATPase, chaperone, or nucleic-acid-binding repertoire; transfer from a rodent record is unsafe without direct mechanistic evidence. Propagation Review Root cause: PROPAGATION BAD Failure modes: FUNCTIONAL DIVERGENCE Sources checked: UniProtKB:Q8CGK3 SUPPORTS SOURCE BUT NOT TARGET ensembl:ENSMUSP00000041814 SUPPORTS SOURCE BUT NOT TARGET |
| GO:0043560 insulin receptor substrate binding | IEA GO_REF:0000107 | REMOVE | Summary: Ortholog-transferred partner-class binding claim lacks human support. Reason: Insulin receptor substrate binding is not supported by the human LONP1 literature or its mitochondrial matrix role, so a rodent interaction phenotype should not propagate as a conserved molecular activity. Propagation Review Root cause: PROPAGATION BAD Failure modes: CONTEXT OR TISSUE MISMATCH FUNCTIONAL DIVERGENCE Sources checked: UniProtKB:Q8CGK3 SUPPORTS SOURCE BUT NOT TARGET ensembl:ENSMUSP00000041814 SUPPORTS SOURCE BUT NOT TARGET |
| GO:0065003 protein-containing complex assembly | IEA GO_REF:0000107 | MODIFY | Summary: Generic complex assembly obscures the demonstrated protein-folding role. Reason: Human LONP1 directly acts as an ATP-dependent chaperone with mtHSP70 (PMID:33431889); de novo protein folding is the better-supported process. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: ROLE CONFLATION GRANULARITY MISMATCH Sources checked: UniProtKB:Q924S5 SUPPORTS SOURCE BUT NOT TARGET ensembl:ENSRNOP00000066618 SUPPORTS SOURCE BUT NOT TARGET Proposed replacements: 'de novo' protein folding |
| GO:0035694 mitochondrial protein catabolic process | TAS Reactome:R-HSA-9837999 | ACCEPT | Summary: Core mitochondrial substrate-degradation process represented in Reactome. Reason: This pathway-level assignment is consistent with direct degradation of oxidized aconitase and imported DELE1 by matrix LONP1 (PMID:12198491; PMID:37327776). |
| GO:0005759 mitochondrial matrix | IMP PMID:33431889 LONP1 and mtHSP70 cooperate to promote mitochondrial protein... | ACCEPT | Summary: Experimentally supported active localization in the mitochondrial matrix. Reason: The full-text study analyzes LONP1 as a matrix AAA+ protease functioning with the mitochondrial mtHSP70 folding system (PMID:33431889). |
| GO:0006458 'de novo' protein folding | IMP PMID:33431889 LONP1 and mtHSP70 cooperate to promote mitochondrial protein... | ACCEPT | Summary: Directly supported ATPase-dependent chaperone role in mitochondrial protein folding. Reason: LONP1 inhibition causes aggregation, and LONP1 cooperates with mtHSP70 to stabilize a folding intermediate; the ATPase rather than protease activity is required (PMID:33431889). |
| GO:0140662 ATP-dependent protein folding chaperone | IMP PMID:33431889 LONP1 and mtHSP70 cooperate to promote mitochondrial protein... | ACCEPT | Summary: Directly demonstrated ATP-dependent protein-folding chaperone activity. Reason: Full-text in-cell and in-vitro experiments establish intrinsic chaperone activity and ATPase-dependent cooperation with mtHSP70 (PMID:33431889). The preserved extension correctly places this activity in de novo protein folding. |
| GO:0005739 mitochondrion | IDA GO_REF:0000052 | KEEP AS NON CORE | Summary: Valid experimental mitochondrial localization, though the matrix child term is more precise. Reason: Immunofluorescence curation supports mitochondrial localization, consistent with older direct localization evidence (PMID:8248235); other annotations specify the mitochondrial matrix. |
| GO:0004252 serine-type endopeptidase activity | EXP PMID:14739292 DNA and RNA binding by the mitochondrial lon protease is reg... | ACCEPT | Summary: Core serine endopeptidase activity supported by catalytic-mutant and substrate assays. Reason: The study directly assays protease function and shows that a protease/ATPase-deficient LONP1 mutant alters substrate-regulated behavior (PMID:14739292), consistent with the established Lon serine protease catalytic center. |
| GO:0004252 serine-type endopeptidase activity | EXP PMID:17420247 Roles for the human ATP-dependent Lon protease in mitochondr... | ACCEPT | Summary: Core catalytic serine endopeptidase activity. Reason: The curated experimental paper studies human ATP-dependent Lon protease catalytic activity in the context of mitochondrial DNA maintenance (PMID:17420247); the term is appropriately specific. |
| GO:0035694 mitochondrial protein catabolic process | IDA PMID:37327776 A mitochondrial iron-responsive pathway regulated by DELE1. | ACCEPT | Summary: Directly demonstrated mitochondrial protein degradation using DELE1 as substrate. Reason: Full-text experiments show that imported DELE1 is degraded by matrix-resident LONP1 under steady-state conditions (PMID:37327776). |
| GO:0005739 mitochondrion | HTP PMID:34800366 Quantitative high-confidence human mitochondrial proteome an... | KEEP AS NON CORE | Summary: High-throughput mitochondrial proteome evidence supports localization. Reason: The quantitative mitochondrial proteome study supports organelle localization (PMID:34800366), while multiple studies localize active mature LONP1 more specifically to the matrix. |
| GO:0004176 ATP-dependent peptidase activity | IDA PMID:37327776 A mitochondrial iron-responsive pathway regulated by DELE1. | ACCEPT | Summary: Direct substrate-specific demonstration of ATP-dependent peptidase activity in mitochondria. Reason: LONP1 degrades imported DELE1 in the mitochondrial matrix (PMID:37327776). The preserved extensions accurately identify DELE1 as input and locate the activity within mitochondrial protein catabolism in mitochondria. |
| GO:0005739 mitochondrion | IDA PMID:8248235 A human mitochondrial ATP-dependent protease that is highly ... | KEEP AS NON CORE | Summary: Foundational direct evidence for mitochondrial localization. Reason: Immunofluorescence in cultured human cells showed predominantly mitochondrial localization (PMID:8248235); matrix annotations provide the more precise compartment. |
| GO:0004176 ATP-dependent peptidase activity | TAS Reactome:R-HSA-9838004 | ACCEPT | Summary: Correct core catalytic activity in a Reactome substrate-degradation reaction. Reason: Reactome assigns LONP1-mediated degradation of mitochondrial inner-membrane proteins; ATP-dependent peptidase activity is the established catalytic function of LONP1. |
| GO:0004176 ATP-dependent peptidase activity | TAS Reactome:R-HSA-9838081 | ACCEPT | Summary: Correct core catalytic activity in a Reactome matrix-protein degradation reaction. Reason: Reactome's matrix-substrate degradation reaction is consistent with direct biochemical and cellular evidence for ATP-dependent LONP1 proteolysis (PMID:12198491; PMID:37327776). |
| GO:0005759 mitochondrial matrix | TAS Reactome:R-HSA-9837978 | ACCEPT | Summary: Correct matrix localization for the Reactome substrate-binding reaction. Reason: LONP1 is an active mitochondrial matrix protease/chaperone, so the reaction compartment is biologically appropriate. |
| GO:0005759 mitochondrial matrix | TAS Reactome:R-HSA-9838004 | ACCEPT | Summary: Correct matrix localization for LONP1-mediated degradation. Reason: Although substrates may be inner-membrane proteins, the LONP1 catalytic machine is matrix localized and acts on matrix-exposed regions. |
| GO:0005759 mitochondrial matrix | TAS Reactome:R-HSA-9838081 | ACCEPT | Summary: Correct matrix localization for the Reactome matrix-protein degradation reaction. Reason: The compartment agrees with direct human localization and functional evidence (PMID:8248235; PMID:33431889). |
| GO:0005759 mitochondrial matrix | TAS Reactome:R-HSA-9838093 | ACCEPT | Summary: Correct matrix localization for substrate engagement by LONP1. Reason: Binding of matrix substrates occurs in the established active compartment of mature LONP1. |
| GO:0005759 mitochondrial matrix | TAS Reactome:R-HSA-9856668 | ACCEPT | Summary: Correct localization of the LONP1 gene product in a Reactome transcriptional-regulation event. Reason: The regulation occurs at the LONP1 gene, but the encoded protease/chaperone acts in the mitochondrial matrix; Reactome's location assignment is consistent with established biology. |
| GO:0004176 ATP-dependent peptidase activity | IMP PMID:14739292 DNA and RNA binding by the mitochondrial lon protease is reg... | ACCEPT | Summary: Core ATP-dependent protease activity supported by catalytic loss-of-function analysis. Reason: The study compares wild-type LONP1 with a mutant lacking ATPase and protease activities and demonstrates substrate-dependent regulation of the enzyme (PMID:14739292). |
| GO:0042802 identical protein binding | IPI PMID:14739292 DNA and RNA binding by the mitochondrial lon protease is reg... | ACCEPT | Summary: Biologically meaningful self-association of the oligomeric Lon protease. Reason: Human LONP1 forms a homo-oligomeric ring-shaped protease complex, and oligomerization is intrinsic to its catalytic machine (PMID:14739292). |
| GO:0034599 cellular response to oxidative stress | IC PMID:12198491 Lon protease preferentially degrades oxidized mitochondrial ... | KEEP AS NON CORE | Summary: Defensible secondary response annotation inferred from oxidized-protein turnover. Reason: LONP1 loss causes accumulation of oxidatively modified aconitase, supporting participation in the cellular oxidative-stress response (PMID:12198491), while GO:0070407 states the direct core process more precisely. |
| GO:0016020 membrane | HDA PMID:19946888 Defining the membrane proteome of NK cells. | REMOVE | Summary: Membrane-proteome detection does not establish membrane localization for soluble matrix LONP1. Reason: The study itself identified many nonintegral and transiently membrane-associated proteins in its biochemical fraction (PMID:19946888). Mature LONP1 is a mitochondrial matrix enzyme, so the broad membrane call is a fractionation carryover rather than its operative location. |
| GO:0030163 protein catabolic process | IDA PMID:17420247 Roles for the human ATP-dependent Lon protease in mitochondr... | MODIFY | Summary: Experimentally supported protein catabolism, but the term is too broad. Reason: The human enzyme degrades proteins in mitochondria; mitochondrial protein catabolic process is the appropriate compartment-specific term (PMID:17420247). Proposed replacements: mitochondrial protein catabolic process |
| GO:0030163 protein catabolic process | IDA PMID:8248235 A human mitochondrial ATP-dependent protease that is highly ... | MODIFY | Summary: Foundational proteolysis evidence represented by an overly broad process term. Reason: Recombinant human LONP1 degraded alpha-casein in an ATP-dependent manner (PMID:8248235), and the physiological enzyme operates in mitochondrial protein catabolism. Proposed replacements: mitochondrial protein catabolic process |
| GO:0070407 oxidation-dependent protein catabolic process | IMP PMID:12198491 Lon protease preferentially degrades oxidized mitochondrial ... | ACCEPT | Summary: Directly supported selective degradation of oxidatively damaged mitochondrial proteins. Reason: LONP1 preferentially recognizes and degrades mildly oxidized aconitase, and LONP1 knockdown reduces aconitase turnover and causes oxidized-protein accumulation (PMID:12198491). |
| GO:0001018 mitochondrial promoter sequence-specific DNA binding | IDA NOT PMID:9485316 The human LON protease binds to mitochondrial promoters in a... | ACCEPT | Summary: The NOT annotation correctly distinguishes single-stranded promoter-element binding from double-stranded promoter binding. Reason: GO:0001018 descends from GO:1990837 sequence-specific double-stranded DNA binding. PMID:9485316 reports that human LONP1 binds the TG-rich promoter element only when it is single stranded, so the negated double-stranded promoter-binding assertion is precise and complements the positive single-stranded DNA-binding annotations. |
| GO:0042645 mitochondrial nucleoid | IDA PMID:18063578 The layered structure of human mitochondrial DNA nucleoids. | UNDECIDED | Summary: Curated nucleoid localization cannot be verified from the available abstract. Reason: PMID:18063578 describes core and peripheral mitochondrial nucleoid proteins but its cached abstract does not name LONP1, and the full text is unavailable here. Consistent with curator-deference policy, this experimental annotation is left undecided rather than rejected. |
| GO:0005515 protein binding | IPI PMID:14739292 DNA and RNA binding by the mitochondrial lon protease is reg... | MARK AS OVER ANNOTATED | Summary: A real TWNK interaction expressed as the uninformative generic protein-binding term. Reason: Co-immunoprecipitation supports interaction of LONP1 with the Twinkle helicase (PMID:14739292), but GO:0005515 does not specify the partner class or functional consequence and should not represent a core molecular function. |
| GO:0070182 DNA polymerase binding | IPI PMID:14739292 DNA and RNA binding by the mitochondrial lon protease is reg... | KEEP AS NON CORE | Summary: Specific interaction with mitochondrial DNA polymerase gamma, with uncertain functional consequence. Reason: Co-immunoprecipitation demonstrates interaction with POLG in the mitochondrial nucleoid context (PMID:14739292). This is informative partner-class binding, but its mechanistic role remains less established than proteolysis and nucleic-acid binding. |
| GO:0001666 response to hypoxia | IEP PMID:17418790 HIF-1 regulates cytochrome oxidase subunits to optimize effi... | KEEP AS NON CORE | Summary: Direct human expression evidence for a contextual hypoxia response. Reason: HIF-1 activates LON expression under hypoxia, enabling COX4-1 degradation during adaptive COX4 subunit switching (PMID:17418790). This is a regulated context rather than LONP1's constitutive core activity. |
| GO:0005759 mitochondrial matrix | IMP PMID:12198491 Lon protease preferentially degrades oxidized mitochondrial ... | ACCEPT | Summary: Correct active localization in the mitochondrial matrix. Reason: The study explicitly describes LONP1 as a mitochondrial matrix protein and examines degradation of matrix aconitase (PMID:12198491). |
| GO:0007005 mitochondrion organization | IMP PMID:15683722 Downregulation of the human Lon protease impairs mitochondri... | KEEP AS NON CORE | Summary: Direct loss-of-function evidence for a broad downstream mitochondrial-organization phenotype. Reason: LONP1 downregulation produces severe defects in mitochondrial morphology, function, mass, and division (PMID:15683722), but these pleiotropic consequences remain secondary to its matrix protease and chaperone activities. |
| GO:0034599 cellular response to oxidative stress | IDA PMID:17420247 Roles for the human ATP-dependent Lon protease in mitochondr... | KEEP AS NON CORE | Summary: Supported secondary role in oxidative-stress biology. Reason: The cited mtDNA-maintenance study examines LONP1 under oxidative stress (PMID:17420247), and independent human evidence establishes LONP1-dependent removal of oxidized aconitase (PMID:12198491). The direct oxidation-dependent catabolic term is more informative. |
| GO:0003727 single-stranded RNA binding | IDA PMID:14739292 DNA and RNA binding by the mitochondrial lon protease is reg... | KEEP AS NON CORE | Summary: Directly demonstrated GU-rich single-stranded RNA binding, with unresolved physiological importance. Reason: Purified human LONP1 specifically interacts with GU-rich RNA in vitro (PMID:14739292), but the in-vivo role of this binding remains less established than its protease and chaperone functions. |
| GO:0004176 ATP-dependent peptidase activity | IDA PMID:17420247 Roles for the human ATP-dependent Lon protease in mitochondr... | ACCEPT | Summary: Directly supported core ATP-dependent peptidase activity. Reason: The study experimentally analyzes the catalytic activity of human ATP-dependent Lon protease in mitochondrial DNA maintenance (PMID:17420247). |
| GO:0004176 ATP-dependent peptidase activity | IDA PMID:8248235 A human mitochondrial ATP-dependent protease that is highly ... | ACCEPT | Summary: Foundational direct demonstration of ATP-dependent proteolysis by human LONP1. Reason: Recombinant truncated human LONP1 degraded alpha-casein in vitro in an ATP-dependent manner (PMID:8248235). |
| GO:0005524 ATP binding | IDA PMID:14739292 DNA and RNA binding by the mitochondrial lon protease is reg... | KEEP AS NON CORE | Summary: True but generic nucleotide-binding subactivity. Reason: Nucleotide-dependent regulation and ATPase/protease mutant analysis support ATP binding (PMID:14739292), but ATP hydrolysis and ATP-dependent peptidase/chaperone activities are more functionally informative. |
| GO:0043531 ADP binding | IDA PMID:14739292 DNA and RNA binding by the mitochondrial lon protease is reg... | KEEP AS NON CORE | Summary: Experimentally observed nucleotide binding that is mechanistically secondary. Reason: ADP-dependent effects on LONP1 nucleic-acid and substrate interactions support binding (PMID:14739292), but this is a subactivity of the AAA+ ATPase cycle rather than a standalone core function. |
| GO:0043565 sequence-specific DNA binding | IDA PMID:14739292 DNA and RNA binding by the mitochondrial lon protease is reg... | MODIFY | Summary: Sequence selectivity is real, but the term omits the experimentally decisive single-stranded substrate constraint. Reason: Human LONP1 binds GT-rich mitochondrial DNA specifically as single-stranded DNA (PMID:14739292; PMID:9485316), so sequence-specific single-stranded DNA binding preserves both demonstrated properties. Proposed replacements: sequence-specific single stranded DNA binding |
| GO:0051880 G-quadruplex DNA binding | IDA PMID:18174225 Thermodynamic characterization of specific interactions betw... | KEEP AS NON CORE | Summary: Direct, specific in-vitro binding activity with uncertain physiological role. Reason: Biochemical and biophysical assays show preferential binding of human LONP1 to parallel G-quartet-forming DNA (PMID:18174225), but the in-vivo consequence remains unresolved. |
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Download this section (compressed HTML)Q: Which client features and LONP1 regulatory states determine folding versus degradation in the mitochondrial matrix?
Q: Does nucleic-acid binding directly couple LONP1 proteolysis to mitochondrial replication or transcription, or does it primarily localize and regulate the protease within nucleoids?
Q: Are isoforms 2 and 3 imported into mitochondria and assembled into active LONP1 oligomers, or do their N-terminal deletions confer distinct localization and function?
Experiment: Reconstitute wild-type LONP1 with matched native, folding-intermediate, mildly oxidized, and aggregated forms of selected clients; quantify ATPase cycling, binding, release, folding, translocation, and cleavage using protease-dead and ATPase-dead controls and with or without the mtHSP70-DNAJA3-GRPEL1 system.
Hypothesis: Client conformation and nucleotide-dependent LONP1 state determine whether a bound protein is released in a folding-competent state or translocated for proteolysis.
Type: biochemical fate-selection reconstitution
Experiment: Rescue LONP1-null human cells with wild-type or nucleic-acid-binding-deficient separation-of-function variants and compare mtDNA/RNA occupancy, TFAM and TWNK turnover, mtDNA replication, transcription, and global matrix proteostasis.
Hypothesis: LONP1 nucleic-acid binding controls local substrate turnover at mitochondrial nucleoids without being required for its general matrix protease activity.
Type: separation-of-function nucleoid analysis
Experiment: Introduce isoform-specific tags at endogenous loci or express matched low-level constructs, then combine live-cell localization, mitochondrial fractionation, protease protection, N-terminomics, and oligomer-resolved native electrophoresis with protease and chaperone rescue assays.
Hypothesis: Isoforms 2 and 3 have reduced mitochondrial import because their N-terminal deletions disrupt the canonical targeting and processing sequence.
Type: isoform-resolved localization and function
What is not known — curated, literature-grounded statements of the open unknowns (the inverse of core functions).
Gap: The molecular features and regulatory states that direct a LONP1-bound client toward productive folding rather than ATP-coupled degradation are unknown.
OPEN BIOLOGY MF_DARK
What is known: LONP1 has directly demonstrated ATP-dependent protease and protease-independent chaperone activities, and OXA1L can behave as a chaperone client in cells while being degraded by wild-type LONP1 in a minimal reconstitution. The unresolved point is how the intact mitochondrial system selects between these outcomes.
Significance: Defining this decision mechanism is necessary to distinguish physiological degradation substrates from folding clients and to interpret substrate-trap or aggregation datasets without conflating the two activities.
What would resolve it: Reconstitute client handling with wild-type and catalytic-separation mutants under controlled nucleotide, phosphorylation, co-chaperone, and client-state conditions, then measure folding, release, translocation, and cleavage in parallel.
Provenance (the field's own admissions):
Gap: The causal physiological role of LONP1 binding to single-stranded mtDNA, promoter sequences, G-quadruplex-prone DNA, and GU-rich RNA remains unresolved.
OPEN BIOLOGY BP_DARK
What is known: Direct biochemical and cellular evidence supports nucleic-acid binding and association with mitochondrial genome control regions. These findings do not yet establish whether nucleic-acid binding recruits particular protein substrates, regulates replication or transcription directly, or mainly tunes LONP1 activity within nucleoids.
Significance: Resolving this would determine whether nucleic-acid binding is a secondary targeting property or a distinct regulatory function with specific mitochondrial gene-expression process annotations.
What would resolve it: Compare nucleic-acid-binding-deficient, ATPase-deficient, and protease-deficient separation-of-function alleles in LONP1-null cells using mtDNA occupancy, replication, transcription, nucleoid dynamics, and substrate-turnover readouts.
Gap: The subcellular localization, processing, oligomerization, and catalytic competence of LONP1 isoforms 2 and 3 are unknown.
OPEN BIOLOGYCURATION CC_DARK
What is known: The canonical isoform contains an N-terminal mitochondrial transit peptide and functions in the matrix. Isoform 2 deletes residues 42-105, overlapping that targeting region, and isoform 3 deletes residues 1-196; no current human GOA source row establishes an isoform-specific localization or activity for either product.
Significance: Without isoform-resolved evidence, canonical matrix localization and the protease/chaperone model must not be propagated automatically to all three splice products.
What would resolve it: Express endogenously tagged isoforms at physiological levels and quantify import, processing, matrix protease protection, homo-oligomer assembly, ATPase, protease, and chaperone activity relative to isoform 1.
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