dsbE

Summary: CcmG forms a disulfide-linked reaction complex with the N-terminal periplasmic domain of DsbD, whose crystal structure was solved.

Reason: The DsbD-CcmG interaction is a genuine redox-reaction intermediate: DsbD reduces CcmG by direct disulfide exchange. Generic protein binding conveys none of this; the functional content is captured by CcmG's protein-disulfide reductase activity and its role in cytochrome c-heme linkage. Removal does not dispute the interaction.

Summary: CcmG is anchored in the inner (plasma) membrane by an N-terminal helix.

Reason: Experimentally shown to be membrane bound with the C-terminal domain in the periplasm; the membrane anchor is part of how CcmG operates in the membrane-associated maturation machinery.

Summary: The Membranome database classifies DsbE as a single-pass (bitopic) membrane protein.

Reason: The computational assignment agrees with direct experimental evidence that CcmG is membrane bound in E. coli.

Summary: CcmG supplies protein-disulfide reducing activity during maturation.

Reason: Protein-disulfide reductase activity is the supported specific descendant. Purified leaderless E. coli DsbE weakly reduces insulin; direct apocytochrome/mixed-disulfide kinetics are established for R. capsulatus, and the P. aeruginosa study considers a mixed-disulfide physiological substrate. These support reductase chemistry without asserting the exact substrate pair has been assayed in every species. The E. coli evidence is distinguished from heterologous ortholog assays and engineered expression constructs.

Proposed replacements: protein-disulfide reductase activity

Summary: CcmG supplies protein-disulfide reducing activity during maturation.

Reason: Protein-disulfide reductase activity is the supported specific descendant. Purified leaderless E. coli DsbE weakly reduces insulin; direct apocytochrome/mixed-disulfide kinetics are established for R. capsulatus, and the P. aeruginosa study considers a mixed-disulfide physiological substrate. These support reductase chemistry without asserting the exact substrate pair has been assayed in every species. The E. coli evidence is distinguished from heterologous ortholog assays and engineered expression constructs.

Proposed replacements: protein-disulfide reductase activity

Summary: CcmG supplies protein-disulfide reducing activity during maturation.

Reason: Protein-disulfide reductase activity is the supported specific descendant. Purified leaderless E. coli DsbE weakly reduces insulin; direct apocytochrome/mixed-disulfide kinetics are established for R. capsulatus, and the P. aeruginosa study considers a mixed-disulfide physiological substrate. These support reductase chemistry without asserting the exact substrate pair has been assayed in every species. The E. coli evidence is distinguished from heterologous ortholog assays and engineered expression constructs.

Proposed replacements: protein-disulfide reductase activity

Summary: CcmG supplies protein-disulfide reducing activity during maturation.

Reason: Protein-disulfide reductase activity is the supported specific descendant. Purified leaderless E. coli DsbE weakly reduces insulin; direct apocytochrome/mixed-disulfide kinetics are established for R. capsulatus, and the P. aeruginosa study considers a mixed-disulfide physiological substrate. These support reductase chemistry without asserting the exact substrate pair has been assayed in every species. The E. coli evidence is distinguished from heterologous ortholog assays and engineered expression constructs.

Proposed replacements: protein-disulfide reductase activity

Summary: PAINT assigns the CcmG/DsbE clade to cytochrome c assembly.

Reason: The node placement is correct (E. coli DsbE is the experimental grounding for the clade), but GO:0017004 is a broad term. CcmG acts in the reductive preparation of apocytochrome CXXCH motifs before the CcmF/CcmH lyase attaches heme; it does not form the heme linkage itself, so GO:1903607 cytochrome c biosynthetic process is the right level, as in the PTHR42852 family review and the sibling Ccm reviews.

Proposed replacements: cytochrome c biosynthetic process

Summary: Electronic annotation from the DsbE family signature.

Reason: Same claim as the IBA and IMP rows; refined to GO:1903607 cytochrome c biosynthetic process for consistency.

Proposed replacements: cytochrome c biosynthetic process

Summary: An in-frame ccmG deletion abolishes all c-type cytochromes; active-site cysteine mutants retain low maturation that is enhanced by exogenous thiols.

Reason: The phenotype is loss of covalent heme attachment to apocytochromes, and the cysteine-mutant/thiol-rescue data place CcmG directly in the reductive preparation of the heme-binding site. CcmG does not attach heme (that is done by CcmF/CcmH), so the specific process is GO:1903607 cytochrome c biosynthetic process rather than cytochrome c-heme linkage.

Proposed replacements: cytochrome c biosynthetic process

Summary: The catalytic thioredoxin domain of CcmG faces the periplasm.

Reason: The membrane-anchored protein's active thioredoxin domain resides in the periplasm, where it reduces exported apocytochromes; the periplasmic location is function-defining and complements the plasma membrane annotation.