Low molecular weight serine protease inhibitors from insects are proteins with highly conserved sequences.
A low molecular weight protease inhibitor peptide found in ovaries of the desert locust Schistocerca gregaria (SGPI-2), was purified from plasma of the same locust and sequenced. It was named SGCI. It was found active towards chymotrypsin and human leukocyte elastase. SGCI was synthesized using a solid-phase procedure and the sequence of its reactive site for chymotrypsin was determined. Compared with an inhibitor purified earlier from another locust species, the total sequence of SGCI showed 88% identity. In particular, the sequence of the reactive site of these inhibitors was identical. Our search for a closely related peptide in an insect species far removed from locusts, the lepidopteran Spodoptera littoralis, was unfruitful but a different chymotrypsin inhibitor, belonging to the Kazal family, was found whose mass is greater than that of SGCI (20 vs 3.6 kDa). Its N-terminal sequence shares 80% identity with that of a chymotrypsin inhibitor purified earlier from the haemolymph of another lepidopteran. Conservation of the amino acid sequence in the reactive site seems to be an exception among protease inhibitors.
Boigegrain
R A
RA
Laboratoire de Pathologie Comparée, INRA-CNRS, UMR 5087, Montpellier, France.
Pugnière
M
M
Paroutaud
P
P
Castro
B
B
Brehélin
M
M
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002918:Chymotrypsin / Q000037:antagonists & inhibitors; D017124:Conserved Sequence; D006110:Grasshoppers / Q000737:chemistry / Q000235:genetics; D006801:Humans; D066298:In Vitro Techniques; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification*; D007313:Insecta / Q000737:chemistry* / Q000235:genetics; D019272:Leukocyte Elastase / Q000037:antagonists & inhibitors; D008969:Molecular Sequence Data; D008970:Molecular Weight; D017386:Sequence Homology, Amino Acid; D015842:Serine Proteinase Inhibitors / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification*; D018411:Spodoptera / Q000737:chemistry / Q000235:genetics
D019476:Insect Proteins; D015842:Serine Proteinase Inhibitors; D002918:Chymotrypsin; D019272:Leukocyte Elastase