PLI (score 0): nematode sperm-MSP function is transferred to a membrane-anchored VAPA protein.
ProtNLM A0A3Q2H1L9, frozen API snapshot 2026-09-08.
Central component in molecular interactions underlying sperm crawling. Forms an extensive filament system that extends from sperm villipoda, along the leading edge of the pseudopod
Both sperm crawling and the villipodial/pseudopod filament system describe the nematode major-sperm-protein motility system. PMID:14565983(https://pubmed.ncbi.nlm.nih.gov/14565983/) experimentally dissects Ascaris MSP-based amoeboid locomotion. This is a specific homologous-domain functional transfer, not a generic statement about a mammalian sperm protein.
Horse VAPA instead retains a cytoplasmic MSP domain at residues 14–131, a coiled-coil region and a C-terminal transmembrane helix at 273–293. Its MSP domain is virtually identical to human VAPA, including the experimentally defined FFAT-binding region. The 45-residue horse insertion is in the intervening linker, corresponding to human alternative splicing; it does not convert the protein into a soluble nematode sperm filament subunit. Reproducible alignment.
The primary VAPA structural/biochemical study states: “VAP‐A, VAP‐B, and MOSPD2 are anchored in the ER membrane by a carboxyl‐terminal transmembrane domain with their MSP domain projecting into the cytosol.” It directly tests FFAT recognition and lipid-transfer contact formation (PMID:33124732(https://pubmed.ncbi.nlm.nih.gov/33124732/)). The horse architecture and conservation justify transferring this adaptor mechanism. An MSP-domain name alone does not justify transferring the nematode motility mechanism.
Error type: PARALOG_OVERANNOTATION, used here for functional over-transfer between homologous MSP-domain protein groups. The exact model training donor is unknown. Both atomic motility claims are contradicted by the target architecture and mammalian biological context. No training-set novelty conclusion is made.