A serine protease from the midgut of the bumblebee, Bombus ignitus (Hymenoptera : Apidae): cDNA cloning, gene structure, expression and enzyme activity

A serine protease gene was cloned from the bumblebee, Bombus ignitits. The B. ignitus serine protease (BiSP) gene spans 1702 bp and consists of four introns and five exons coding for 250 amino acid residues. Southern blot analysis of genomic DNA suggested that BiSP gene is a single copy gene. The cDNA encoding BiSP was expressed as a 28-kDa polypeptide in baculovirus-infected insect cells and the recombinant BiSP showed activity in a protease enzyme assay. BiSP was specifically expressed in the midgut of B. ignitus queens, males, and workers, suggesting that the BiSP is a gut enzyme involved in the digestion of dietary proteins.