Sequence analysis and expression characteristics of chemosen⁃ sory protein AmelCSP2 in Apis mellifera

【Objective】To explore the sequence characteristics of the chemosensory protein CSP2 of Apis mellifera （AmelCSP2）and the tissue expression characteristics of the AmelCSP2 gene，which could provide theoretical reference for clarifying the biological function of AmelCSP2 protein.【Method】The physicochemical properties，hydrophilicity/hy‐ drophobicity，signal peptide，transmembrane domain，subcellular localization，O-glycosylation sites，N-glycosylation sites，phosphorylation sites，advanced structure，motif，domain and protein interaction network of AmelCSP2 protein were predicted by using bioinformatics softwares such as ProtParam，ProtScal，SignalP-5.0，TMHMM-2.0，PSORTb 3.0.3，DictyOGlyc-1.1，NetNGlyc-1.0，NetPhos 3.1，SWISS-MODEL，CD-search，SMART and STRING. The relative expression levels of AmelCSP2 gene in the antennae，head（excluding antennae），thorax，abdomen，leg and wing of A. mellifera were detected by real-time fluorescence quantitative PCR.【Result】The AmelCSP2 protein encoded 117 amino acid residues，with a theoretical molecular weight of approximately 13.06 kD，a theoretical isoelectric point（pI）of 9.27， a molecular fat coefficient of 92.56，an instability coefficient of 59.68，and an average hydrophilicity index of -0.254， being an amphoteric and unstable protein. The AmelCSP2 protein had a signal peptide at amino acid residues positions 1-21， did not contain transmembrane domain，and was mainly located in the periplasm，cytoplasm and extracellular membrane. The AmelCSP2 protein had no glycosylation sites but had 20 phosphorylation sites. In the secondary structure of AmelCSP2 protein，random coils accounted for 42.74%，α-helices accounted for 38.46%，and extended chains accounted for 18.80%，and the tertiary structure of the protein was relatively stable. The AmelCSP2 protein belonged to the OS-D superfamily and had the only protein domain OS-D at amino acid residues positions 32-116. The AmelCSP2 protein might interact with PYX2，ASP3，OBP3c，NT-7 and OBP14 proteins. The AmelCSP2 gene was expressed in the antennae，head （excluding antennae），thorax，abdomen，leg and wing of A. mellifera，and the relative expression level of the AmelCSP2 gene in the antennae was significantly higher than that in other tissues（P<0.05）.【Conclusion】AmelCSP2 protein has a typical OS-D superfamily domain and contains multiple phosphorylation sites，which may regulate its function through phosphorylation modification. AmelCSP2 protein may interact with PYX2，ASP3，OBP3c，NT-7 and OBP14 proteins and participate in chemical sensory signal transduction. AmelCSP2 gene is highly expressed in the antennae of A. mellifera，and may play the role of odor molecule transport in the olfactory perception system.