Affinage

PMPCA

Mitochondrial-processing peptidase subunit alpha · UniProt Q10713

Length
525 aa
Mass
58.3 kDa
Annotated
2026-06-10
11 papers in source corpus 8 papers cited in narrative 8 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 5/5 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

PMPCA encodes α-MPP, one of the two non-identical subunits of the mitochondrial matrix processing peptidase (MPP), a zinc-metalloprotease that cleaves N-terminal presequences from nuclear-encoded mitochondrial precursor proteins upon import (PMID:2905264, PMID:3061808). Originally defined in yeast as the MAS2 gene product, α-MPP is a matrix-localized protein homologous to its partner subunit MAS1/PMPCB, and the two subunits are loosely associated yet jointly required for proteolytic activity—separation or mutation of either abolishes presequence cleavage (PMID:2905264, PMID:3061808). In humans, α-MPP catalyzes maturation of mitochondrial substrates including frataxin, and biallelic PMPCA mutations that lower α-MPP protein levels impair frataxin processing, a defect reversed by re-expression of wild-type PMPCA (PMID:25808372, PMID:27148589). Beyond proteolytic maturation, loss of α-MPP perturbs mitochondrial network morphology—producing either hyperconnected or fragmented mitochondria—without overtly disrupting the respiratory chain, indicating a role in mitochondrial morphodynamics (PMID:35885985, PMID:38235041). Disease-causing PMPCA variants underlie an autosomal recessive disorder featuring defective frataxin maturation, and frameshift variants are associated with dominant optic atrophy phenotypes (PMID:25808372, PMID:27148589, PMID:35885985). α-MPP itself is synthesized as an inactive larger precursor that is processed to a smaller mature form on which MPP enzymatic activity depends (PMID:20019080).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 1988 High

    Established that the mitochondrial presequence-cleaving protease is a two-subunit enzyme and identified the larger subunit as the MAS2 (PMPCA) gene product, defining α-MPP as a required component of MPP activity.

    Evidence Native metalloprotease purification, SDS-PAGE subunit identification, and genetic complementation in yeast

    PMID:2905264 PMID:3061808

    Open questions at the time
    • Catalytic contribution of each subunit not resolved
    • Structural basis of presequence recognition not defined
  2. 1988 High

    Localized the MAS2/α-MPP subunit to the mitochondrial matrix and directly tied it to catalysis by showing temperature-sensitive loss of protease activity in mas2 mutants.

    Evidence Gene cloning/sequencing, ts-mutant analysis, subcellular fractionation, and activity assays in yeast

    PMID:3061808

    Open questions at the time
    • Human substrate repertoire not yet established
    • Mechanism of subunit cooperativity unknown
  3. 2009 Medium

    Showed that α-MPP requires conversion from a larger precursor form to a smaller mature form for MPP activity, identifying autoregulatory processing as a control point.

    Evidence Antisense suppression, western blot for α-MPP forms, and enzymatic activity assays across Dictyostelium development

    PMID:20019080

    Open questions at the time
    • Protease responsible for α-MPP maturation not identified
    • Relevance of precursor processing in human cells untested
  4. 2015 Medium

    Connected human PMPCA to disease and to frataxin biology by showing a recessive mutation lowers α-MPP levels and impairs frataxin processing.

    Evidence Western blot and functional assays in patient lymphoblastoid cells and fibroblasts carrying p.Ala377Thr

    PMID:25808372

    Open questions at the time
    • Single mutation; full substrate spectrum unaddressed
    • No rescue performed in this study
  5. 2016 Medium

    Confirmed causality of α-MPP loss in frataxin maturation defects by rescuing patient cells with wild-type PMPCA cDNA.

    Evidence Immunofluorescence, western blot, and complementation rescue in patient fibroblasts

    PMID:27148589

    Open questions at the time
    • Structural impact of glycine-rich loop variants not modeled
    • Broader proteome processing defects not quantified
  6. 2017 Medium

    Placed the PMPCA ortholog within the mitochondrial import pathway by linking it to Hsp40 chaperone Ydj1, which acts upstream of Mas1/Mas2 in substrate import and processing.

    Evidence Co-purification/MS interaction mapping, gene deletion, and Su9 import/processing assays in Candida albicans

    PMID:29082232

    Open questions at the time
    • Interaction not validated in human cells
    • Whether Ydj1 directly hands off substrates to MPP unresolved
  7. 2022 Medium

    Demonstrated a role for α-MPP in mitochondrial morphodynamics distinct from respiration, with frameshift variants causing network hyperconnection.

    Evidence Western blot and confocal microscopy of mitochondrial morphology in DOA patient fibroblasts

    PMID:35885985

    Open questions at the time
    • Mechanism linking MPP activity to fusion-fission balance unknown
    • No rescue experiment
  8. 2023 Low

    Extended the genotype-phenotype range, showing additional compound heterozygous variants reduce α-MPP and cause reduced, fragmented mitochondria.

    Evidence Western blot and confocal microscopy in patient skin fibroblasts

    PMID:38235041

    Open questions at the time
    • No mechanistic rescue or pathway placement beyond protein reduction
    • Opposite morphology direction versus prior report unexplained

Open questions

Synthesis pass · forward-looking unresolved questions
  • How α-MPP loss mechanistically reshapes the mitochondrial network, and the identity of the human protease maturing α-MPP itself, remain open.
  • No structural model of human MPP holoenzyme
  • Full human substrate proteome of MPP undefined
  • Link between processing defects and morphology phenotypes uncharacterized

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140096 catalytic activity, acting on a protein 4 GO:0016787 hydrolase activity 2
Localization
GO:0005739 mitochondrion 2
Pathway
R-HSA-392499 Metabolism of proteins 4 R-HSA-9609507 Protein localization 1
Partners
PMPCBYDJ1
Complex memberships
mitochondrial processing peptidase (MPP)

Evidence

Reading pass · 8 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1988 The yeast mitochondrial matrix processing protease (MPP) consists of two non-identical, loosely associated subunits of ~48 kDa (MAS1/PMPCB) and ~51 kDa (MAS2/PMPCA); the larger subunit is the product of the MAS2 gene, and attempts to separate the two subunits caused loss of proteolytic activity, indicating both subunits are required for function. Purification of native metalloprotease complex, SDS-PAGE subunit identification, genetic complementation (MAS2 gene identification) The EMBO journal High 2905264 3061808
1988 MAS2 (PMPCA ortholog) encodes a 53-kDa protein localized to the mitochondrial matrix; it is homologous to MAS1 (PMPCB) and together they constitute the two subunits of the presequence-cleaving processing protease. The protease activity is temperature-sensitive in mas2 mutant cells, directly linking the MAS2 subunit to catalytic function. Gene cloning and sequencing, temperature-sensitive mutant analysis, subcellular fractionation/localization, enzymatic activity assay in mutant cells The EMBO journal High 3061808
2015 Human PMPCA (α-MPP) is the alpha subunit of the mitochondrial processing peptidase responsible for maturation of nuclear-encoded mitochondrial proteins; the disease-associated p.Ala377Thr mutation reduces α-MPP protein levels and impairs MPP function, including defective processing of frataxin in patient lymphoblastoid cells and fibroblasts. Western blot and functional assays in patient-derived lymphoblastoid cells and fibroblasts carrying homozygous PMPCA p.Ala377Thr mutation Brain : a journal of neurology Medium 25808372
2016 Compound heterozygous mutations in PMPCA near the substrate-binding glycine-rich loop reduce α-MPP protein levels and impair frataxin production and processing in patient fibroblasts; these defects were rescued by expression of exogenous wild-type PMPCA cDNA, confirming the causal role of α-MPP in frataxin maturation. Immunofluorescence, western blot in patient fibroblasts, rescue experiment with exogenous wild-type PMPCA cDNA expression Cold Spring Harbor molecular case studies Medium 27148589
2009 In Dictyostelium discoideum, α-MPP is synthesized as a larger precursor form (α-MPP(H)) that is cleaved to produce a smaller functional form (α-MPP(L)); MPP enzymatic activity depends on the presence of α-MPP(L), as antisense-suppressed cells retaining only α-MPP(H) showed no detectable MPP activity, and activity was restored upon reappearance of α-MPP(L). Antisense transformant analysis, western blot for α-MPP forms, MPP enzymatic activity assay during Dictyostelium development Microbiology (Reading, England) Medium 20019080
2017 In Candida albicans, the Hsp40 chaperone Ydj1 physically interacts with the mitochondrial processing peptidases Mas1 and Mas2 (orthologs of PMPCB and PMPCA), and loss of MAS2 perturbs mitochondrial morphology and function; deletion of YDJ1 impairs import and processing of Su9, a substrate cleaved by Mas1/Mas2, placing PMPCA ortholog Mas2 downstream of Ydj1 in the mitochondrial import pathway. Protein interaction network mapping (co-purification/MS), genetic deletion analysis, mitochondrial morphology and function assays, import/processing assay for Su9 substrate Microbial cell (Graz, Austria) Medium 29082232
2022 Frameshift PMPCA variants in DOA patients reduce α-MPP protein levels in fibroblasts and cause hyperconnection of the mitochondrial network (altered fusion-fission balance), without significantly affecting the respiratory chain machinery, indicating α-MPP influences mitochondrial morphodynamics independently of respiratory function. Western blot for α-MPP levels, immunofluorescence confocal microscopy of mitochondrial network morphology in patient fibroblasts Genes Medium 35885985
2023 Novel compound heterozygous PMPCA variants (p.Tyr241Ser and p.Met251Val) decrease α-MPP protein levels and result in reduced and fragmented mitochondria in patient fibroblasts, linking α-MPP loss to mitochondrial morphology defects. Western blot for α-MPP levels, immunofluorescent confocal microscopy of mitochondrial morphology in patient skin fibroblasts Neurology. Genetics Low 38235041

Source papers

Stage 0 corpus · 11 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
1988 Import of proteins into yeast mitochondria: the purified matrix processing protease contains two subunits which are encoded by the nuclear MAS1 and MAS2 genes. The EMBO journal 191 2905264
1988 Import of proteins into yeast mitochondria: the nuclear MAS2 gene encodes a component of the processing protease that is homologous to the MAS1-encoded subunit. The EMBO journal 129 3061808
2015 PMPCA mutations cause abnormal mitochondrial protein processing in patients with non-progressive cerebellar ataxia. Brain : a journal of neurology 62 25808372
2010 Purification and characterization of an extracellular laccase from the anthracene-degrading fungus Fusarium solani MAS2. Bioresource technology 55 20716485
2016 Mutations in the substrate binding glycine-rich loop of the mitochondrial processing peptidase-α protein (PMPCA) cause a severe mitochondrial disease. Cold Spring Harbor molecular case studies 35 27148589
2017 Ydj1 governs fungal morphogenesis and stress response, and facilitates mitochondrial protein import via Mas1 and Mas2. Microbial cell (Graz, Austria) 30 29082232
2020 A severe form of autosomal recessive spinocerebellar ataxia associated with novel PMPCA variants. Brain & development 11 33272776
2022 Next-Generation Sequencing Identifies Novel PMPCA Variants in Patients with Late-Onset Dominant Optic Atrophy. Genes 3 35885985
2009 Mitochondrial processing peptidase activity is controlled by the processing of alpha-MPP during development in Dictyostelium discoideum. Microbiology (Reading, England) 3 20019080
2023 PMPCA-Related Encephalopathy: Novel Variants, Phenotype Extension, and Mitochondrial Morphology. Neurology. Genetics 2 38235041
2024 Clinical whole Exome Sequencing Reveals Novel Homozygous Missense Variant in the PMPCA Gene causing Autosomal Recessive Spinocerebellar Ataxia. Pakistan journal of medical sciences 0 39554679

Missed literature

Know a paper Affinage missed for PMPCA? Flag it for the maintainers and the community.

No submissions yet.