Niemann-Pick Type C2 Proteins in Aedes aegypti : Molecular Modelling and Prediction of Their Structure-Function Relationships.

Aedes aegypti is a major vector that transmits arboviruses through the saliva injected into the host. Salivary proteins help in uninterrupted blood intake and enhance the transmission of pathogens. We studied Niemann-Pick Type C2 (NPC2) proteins, a superfamily of saliva proteins that play an important role in arbovirus infections. In vertebrates, a single conserved gene encodes for the NPC2 protein that functions in cholesterol trafficking. Arthropods, in contrast, have several genes that encode divergent NPC2 proteins. We compared the sequences of 20 A. aegypti NPC2 proteins to the cholesterol-binding residues of human and bovine, and fatty-acid-binding residues of ant NPC2 protein. We identified four mosquito NPC2 proteins as potential sterol-binding proteins. Two of these proteins (AAEL006854 and/or AAEL020314) may play a key role in ecdysteroid biosynthesis and moulting. We also identified one mosquito NPC2 protein as a potential fatty-acid-binding protein. Through molecular modelling, we predicted the structures of the potential sterol- and fatty-acid-binding proteins and compared them to the reference proteins.