Homologues
MSP genes have been identified across widely diverged nematode species. They all have more than 60% sequence identity.
Proteins with limited sequence similarity were identified in species from plants to mammals. One of the homologues is VAP33 from Aplysia californica. VAP33 is a protein required for neurotransmitter release, which binds to the v-SNARE synaptobrevin/VAMP, associated with vesicle fusion.
Despite only 11% of sequence similarity, MSP and the N-terminus of the bacterial P-pilus associated chaperonin PapD share a high structural and topological homology in their β sheet regions. Both MSP and PapD can be classified to the s-type immunoglobulin fold proteins, characterized by the above mentioned unique strand switching.
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