THE BIOSYNTHESIS AND PROCESSING OF VITELLOGENIN IN THE FAT-BODIES OF FEMALES AND MALES OF THE COCKROACH LEUCOPHAEA-MADERAE

The juvenile hormone analog (JHA) methoprene was used to induce the sy nthesis of the yolk protein precursor vitellogenin (Vg) in adult femal es and;males of the cockroach Leucophaea maderae. The female-and male- produced vitellogenin !(VgF and VgM, respectively) contained polypepti des of 112, 95, 92, and 54 kDa, Also present in the secreted vitelloge nins was a small quantity of a short-lived transitional 155 kDa Vg pol ypeptide, and a variable amount of an 85 kDa species, Quantitatively, the VgF and VgM were significantly different in the Vg112 and Vg95 uni ts (VgF > VgM), and in the Vg85 polypeptide (VgF < VgM), In the presen t study, the biosynthesis of Vg precursors in the fat bodies of female s and males was examined using a short radiopulse with S-35-methionine /cysteine and P-32-orthophosphate. The glycosylation of the Vg precurs ors was examined by digestion with endoglycosidase H and by the inhibi tion of N-linked glycosylation with tunicamycin. The data showed that in both females and males, the synthesis of the vitellogenin precursor occurred in a stepwise fashion: (1) the co-translational glycosylatio n of Vg203; (2) the post-translational phosphorylation of Vg203 to for m Vg220; (3) the proteolytic processing of Vg220 to form the constitue nt Vg polypeptides. The 203 and 220 kDa Vg precursors of females and m ales appeared to be similarly glycosylated and phosphorylated, The add itional processing of Vg112 to Vg85 was more pronounced in the fat bod ies of males than in females, and appears to account for the quantitat ive difference in the distribution of these polypeptides in VgF and Vg M, Finally, the major oligosaccharides of VgF and VgM appear to be tho se of N-linked mannose residues, The treatment of females and males wi th tunicamycin indicated that the co-translational glycosylation of Vg precursors was required for the phosphorylation of the Vg precursor, as well as the secretion of Vg from the fat body, (C) 1998 Elsevier Sc ience Ltd. All rights reserved.