Two subunits of the insect 26/29-kDa proteinase are probably derived from a common precursor protein.
We previously identified the 26/29-kDa proteinase in the hemocytes of Sarcophaga peregrina (flesh fly) that appears to participate in elimination of foreign proteins in this insect [Eur. J. Biochem. 209, 939-944 (1992)]. Here, we report the cDNA cloning of this proteinase. The cDNA encodes a protein which includes both the 26- and 29-kDa subunit, strongly suggesting that the both subunits are derived from a single precursor protein. The 26- and 29-kDa subunit located at the amino-terminal and carboxyl-terminal of the precursor protein. The 29-kDa subunit itself appeared to be a proteinase, for this subunit had 52% sequence identity with Sarcophaga cathepsin L, while 26-kDa subunit had no significant similarity. We also showed that 26/29-kDa proteinase was insensitive to specific inhibitors of cathepsin L. These results indicate that this proteinase is a novel member of the papain family. We isolated similar cDNAs from Drosophila melanogaster and Periplaneta americana (cockroach), suggesting that this proteinase is conserved in a wide variety of insects and participates in their defense mechanisms.
Faculty of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan.
Y
Y
Fujimoto
A
A
Kobayashi
S
S
Kurata
S
S
Natori
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003546:Cysteine Endopeptidases / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics*; D018076:DNA, Complementary / Q000235:genetics; D004331:Drosophila melanogaster; D007313:Insecta; D008969:Molecular Sequence Data; D010802:Phylogeny; D011498:Protein Precursors / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics*; D016415:Sequence Alignment; D017421:Sequence Analysis
D018076:DNA, Complementary; D011498:Protein Precursors; D003546:Cysteine Endopeptidases