Entomology and Plant Pathology

Aligned sequences of the catalytic domains in Drosophila c-SPs and c-SPHs.

The putative proteolytic activation sites are marked by a I^I. Positions at which a single amino acid residue is present in 13-25 (35-69%) or 26-37 (>70%) of the 37 sequences are marked by “+” or “*”, respectively. The positions shown in a box correspond to the histidine, aspartic acid, and serine residues at the active site. Double lines denote three disulfide bonds that are absolutely conserved in mammalian serine proteases. The remaining cysteine residues are numbered 1-5. Cys- 1 and Cys-2, found in all of the insect prophenoloxidase-activating proteases, are predicted to form a disulfide bridge. A linkage between Cys-4 and Cys-5 may also exist in 13 of the 14 c-SPHs (except for c-SPH64). Cys-3 is expected to pair with a cysteine residue in the regulatory clip domain. The residues that determine the primary specificity binding pocket are marked I@I. The numbers at the carboxyl termini of c-SPH69, c-SP18, c-SP36, and c- SP33 indicate the region that are not included in the sequence alignment.
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