Comparison of venom protease allergens from bees and paper wasps

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Rationale Serine proteases have been found to be allergens in venoms from honeybees, bumblebees and paper wasps. Methods The amino acid sequences determined in our laboratory were analyzed by computer techniques; and 3-dimensional structural models were constructed by Swiss-Model with other protease template structures. Results The serine protease domains of all 3 molecules belonged to subfamily S1A Clan PA(S) enzyme S01, trypsin EC 3.4.21.4. All contained the aspartic acid at the bottom of the substrate pocket which binds lysine or arginine, giving a tryptic specificity. The protease domains of Polistes dominulus (Pd) and Apis mellifera (Am) enzymes are 41.5% identical over 248 residues, Pd is 31.8% identical to Bombus pennsylvanicus (Bp) over 245 residues and AM is 33.1% identical to Bp over 242 residues. The 3 enzymes have different residues at the entrance to the substrate binding pocket. Bp has a glycine, which is the most common in this family; Pd has an asparagine, which is uncommon but found in a number of other family members; and Am has a methionine, which is unique. The Am enzyme also has a CUB domain for protein-protein interaction. All three enzymes are active, but their detailed specificity preferences are unknown. They may each have a specialized role in the venom, possibly activation of another component or peptide. Conclusions Although there is some homology in the venom proteases, it does not follow phylogeny; and each enzyme may have a specialized function in the venom.