The insect immune protein scolexin is a novel serine proteinase homolog

• Published in: Protein science Vol. 8; no. 1; pp. 242 - 248
• Main Authors: FINNERTY, CASEY M., KARPLUS, P. ANDREW, GRANADOS, ROBERT R.
• Format: Journal Article
• Language: English
• Published: Bristol Cambridge University Press 01-01-1999; Cold Spring Harbor Laboratory Press
• Subjects: alignment; Amino Acid Sequence; Animals; Base Sequence; cDNA; Cloning, Molecular; DNA, Complementary; FOR THE RECORD; Glycoproteins - chemistry; Glycoproteins - genetics; Glycoproteins - metabolism; Humans; Hydrolysis; Insect Proteins - chemistry; Insect Proteins - genetics; Molecular Sequence Data; sequence; Sequence Homology, Amino Acid; Serine Endopeptidases - chemistry; Serine Endopeptidases - genetics; Serine Endopeptidases - metabolism; serine proteinase; zymogen activation; sequence; cDNA; alignment; serine proteinase; zymogen activation
• ISSN: 0961-8368; 1469-896X
• DOI: 10.1110/ps.8.1.242

Scolexin is a coagulation-provoking plasma protein
induced in response to bacterial or viral infection of
larval Manduca sexta, a large lepidopterous insect.
Here we report the isolation and sequencing of two cDNA
clones that code for scolexin isoforms sharing 80% sequence
identity. The scolexin sequences have low but recognizable
sequence similarity to members of the chymotrypsin family
and represent a new subfamily of chymotrypsin-like serine
proteinases. Comparison with known structures reveals the
conservation of key catalytic residues and a possible specificity
for small nonpolar residues. Most remarkable is the absence
of a canonical activation peptide cleavage site. This suggests
that the regulation of scolexin activity will involve a
novel activation mechanism.