BIOCHEMICAL-CHARACTERIZATION, DEVELOPMENTAL EXPRESSION, AND INDUCTIONOF THE IMMUNE PROTEIN SCOLEXIN FROM MANDUCA-SEXTA

The immune protein, scolexin, a bacteria-induced, larva-specific prote in from Manduca sexta, was shown to exist in the hemolymph in two isoe lectric forms designated herein as scolexin-1 and scolexin-2 (native M (r) similar to 72 kd). These two charge isomers appeared to share the same amino acid composition. Scolexin is composed of two subunits (pep tide M(r) similar to 36 kd) that possess the same N-terminus. Scolexin -2 was subjected to glycosyl composition analysis, revealing the prese nce of galactose, glucose, mannose, xylose, and sialic acid residues. Hybridization of epidermal RNA with oligonucleotides deduced from the scolexin N-terminal sequence showed a continuous decline in mRNA follo wing day 0 of the 5th larval instar. By employing in vitro protein lab elling, it was found that organ cultures of the epidermis from immune larvae showed a greater ability over that of naive epidermal cultures to synthesize scolexin; these data reflected the inducible response se en in the hemolymph, and confirm other data indicating that the epider mis is an important site of scolexin biosynthesis. (C) 1995 Wiley-Liss , Inc.