author(s)
Kyaw Lin Maung, Dapeng Jing, Tiantao Zhang, Kanglai He, Shuxiao Bai and Zhenying Wang

abstract
Niemann Pick type C2 (NPC2) proteins were identified as olfactory related genes such as odorant carriers in arthropods. NPC2 in Macrocentrus cingulum’s functional characteristics are similar to odorant binding proteins. Recently, we identified NPC2 protein in Macrocentrus cingulum (namely McinNPC2) as a Genbank accession number MK089532.1 at National Center for Biotechnology Information. Comparative evolutionary relationship and primary structures between NPC2 and olfactory proteins such as odorant binding proteins, general odorant binding proteins, pheromone binding proteins (OBPs, GOBPs, PBPs respectively) were performed. Evolutionary relationship results between NPC2 in Ceratosolen solmsi marchali (CsolNPC2) and OBP in Microplitis mediator (MmedOBP), NPC2 in Trachymyrmex septentrionalis (TsepNPC2) and GOBP in Polistes Canadensis (PcanGOBP), NPC2 in Dufourea novaeangliae (DnovNPC2) and PBP in Apis cerana (AcerPBP) were clustered forming one clade as a nearest phylogeny. The identity of CsolNPC2 with MmedOBP, TsepNPC2 and PcanGOBP, DnovNPC2 and AcerPBP are 13.21%, 17.36%, 17.56 % respectively with the similar residues 50.31%, 47.92%, 41.98% respectively. Representative NPC2 alignments in hymenoptera results showed that 6 cysteine consensus amino acids while showing the same 6 cysteine amino acids in an alignment of representative OBPs, GOBPs and PBPs alignments. Unexpectedly, we observed that secondary structure prediction between McinNPC2 and McinOBP1, McinOBP2, McinOBP3, McinOBP4 showed different shade of subphyla. In conclusion, our results reveal that structural characteristics of NPC2 proteins are similar to OBPs, GOBPs and PBPs in hymenoptera.