Summary: Phylogenetic propagation of mitochondrial localization.

Reason: Correct but generic; the intermembrane space and inner membrane rows are more informative.

Summary: Phylogenetic propagation of the complex IV assembly role, seeded partly from this gene's own experimental annotations and from human COA5.

Reason: Directly supported on the target by IMP evidence in two independent studies three decades apart. Core biological process. The gene's own SGD id in the WITH/FROM is expected and correct.

Summary: UniProt-derived intermembrane space localization.

Reason: Consistent with the IDA evidence on the target, including Bax-release IMS proteomics.

Summary: Direct assay inner membrane localization: Pet191 is associated with the inner membrane within a large oligomeric complex.

Reason: A genuine direct observation, and consistent with UniProt's note that Pet191 is imported into the intermembrane space. Best read as peripheral association on the intermembrane space face; the intermembrane space term is the primary compartment.

Summary: High-throughput mitochondrial localization.

Reason: Correct but generic; subsumed by the intermembrane space rows. No supporting_text is attached: the cached record is a proteome-scale survey that does not name this protein in its text, so no verbatim quotation can carry the claim.

Summary: High-throughput mitochondrial localization from a second proteomic survey.

Reason: Same as the other HDA row: correct organelle, subsumed by the sub-compartment evidence. No supporting_text is attached: the cached record is a proteome-scale survey that does not name this protein in its text, so no verbatim quotation can carry the claim.

Summary: SGD's explicit 'no data' placeholder for molecular function.

Reason: Correct and worth preserving. No catalytic or binding activity has been demonstrated for this protein, and the ND placeholder is an accurate statement of the state of knowledge. It should be retired only when a real molecular function is shown, not replaced with a generic binding term. The same honest-unknown pattern holds across COA4, COX23, CMC2 and PET191 - four intermembrane space assembly factors in this pathway whose molecular functions remain genuinely undetermined. For Pet191 specifically, UniProt's description of it stabilizing an early assembly intermediate until displaced by a copper metallochaperone is a model rather than a demonstrated activity, and should not be converted into a chaperone or binding annotation. No supporting_text is attached: this row asserts the absence of demonstrated activity, and no quotation can evidence an absence. The argument for keeping it is the reasoning above, not a citation.

Summary: Direct assay intermembrane space localization by Bax-release proteomics.

Reason: Bax-release IMS proteomics followed by Pet191-specific protease protection directly supports mitochondrial intermembrane-space localization.

Summary: Mutant phenotype evidence that Pet191 is essential for cytochrome c oxidase maturation, with the twin Cx9C motif cysteines functionally important.

Reason: The primary modern characterization of this gene establishes the core complex IV assembly phenotype. Its Mia40-independence model was disputed by later IMS-proteome work, so use the assembly defect rather than the proposed import exception for family-level inference.

Summary: Mutant phenotype evidence from the original cloning of PET191 as a gene required for assembly of active cytochrome c oxidase whose product is not a subunit of the final complex.

Reason: The founding evidence for this gene, and an early explicit statement that Pet191 is an assembly factor rather than a structural subunit.