CEBPZOS (CEBPZ opposite strand) encodes an 80-amino-acid protein from a gene transcribed from the strand opposite CEBPZ; it is the canonical product of its own gene rather than an alternative reading frame of CEBPZ. The protein has a single predicted transmembrane helix near its N-terminus (residues 15-32) followed by a short hydrophilic C-terminal region, and no recognised domain outside its own family (InterPro CEBPZOS family). It is conserved across animals, with Drosophila CG42371 as its fly ortholog. CEBPZOS is a mitochondrial membrane protein: it was captured by proximity labelling from the mitochondrial intermembrane space and confirmed as mitochondrial by imaging or immunoblotting, and it is part of the high-confidence human mitochondrial proteome. Which mitochondrial membrane it occupies and its topology have not been resolved. Its molecular function is unknown. Its abundance rises when mitochondrial DNA is depleted in cultured human cells, and flies lacking CG42371 develop normally on standard food but show reduced viability on high-salt or high-fat diets.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005739 mitochondrion | HTP PMID:34800366 Quantitative high-confidence human mitochondrial proteome an... | ACCEPT | Summary: High-throughput assignment from MitoCoP, a high-confidence human mitochondrial proteome built by combining subtractive, spatial and mitochondria-specific proteomics. The cached text does not name CEBPZOS (the protein list is supplementary), but the row agrees with independent APEX proximity labelling and imaging/immunoblot validation (PMID:25002142). Reason: Correct and independently corroborated. The more specific GO:0031966 mitochondrial membrane is also annotated, but the HTP row records a separate line of evidence and should be kept. Supporting Evidence: PMID:34800366 high-confidence proteome (MitoCoP) of 1,134 protein-coding genes, including 91 proteins previously not localized to mitochondria experimentally PMID:25002142 three proteins of unknown function (A8MTT3, C1orf163, and CCDC127) |
| GO:0031966 mitochondrial membrane | EXP PMID:25002142 Proteomic mapping of the human mitochondrial intermembrane s... | ACCEPT | Summary: CEBPZOS (as A8MTT3) was detected in the ratiometric IMS-APEX proteome of HEK293T cells and was one of nine previously non-mitochondrial proteins validated as mitochondrial by imaging or western blotting. Labelling by IMS-targeted APEX places a segment of the protein in the intermembrane space; with a single predicted transmembrane helix this fits an integral mitochondrial membrane protein. Reason: Best available localization evidence and the appropriate level of specificity. The data do not distinguish inner from outer membrane, so a more specific term is not justified. Supporting Evidence: PMID:25002142 we have identified 9 novel mitochondrial proteins that we validated by imaging or western blotting PMID:25002142 three proteins of unknown function (A8MTT3, C1orf163, and CCDC127) |
| GO:0031966 mitochondrial membrane | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular-location mapping (SL-0171 Mitochondrion membrane). The UniProt location is itself based on PMID:25002142, so this row restates the EXP annotation. Reason: Correct; consistent with the experimental annotation it derives from. Supporting Evidence: PMID:25002142 three proteins of unknown function (A8MTT3, C1orf163, and CCDC127) |
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Download this section (compressed HTML)Q: Is CEBPZOS in the inner or the outer mitochondrial membrane, and which terminus faces the intermembrane space?
Q: Does CEBPZOS associate with a respiratory chain complex, an assembly intermediate or another inner-membrane machine, as several other mitochondrial microproteins do? No such evidence was found.
Q: Is the rise in CEBPZOS protein after mtDNA depletion a specific response (for example, part of the mitochondrial integrated stress response) or a non-specific change?
Experiment: Protease-protection and carbonate-extraction assays on isolated mitochondria and mitoplasts, using epitope tags at either terminus, to assign membrane and topology.
Experiment: Affinity purification or proximity labelling with tagged CEBPZOS, combined with blue-native PAGE, to identify partner complexes; then measure respiration and complex assembly in CEBPZOS-knockout human cells.
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