PROTEOLYTIC PROCESSING OF THE VITELLOGENIN PRECURSOR IN THE BOLL-WEEVIL, ANTHONOMUS-GRANDIS

The soluble proteins of the eggs of the coleopteran insect Anthonomus grandis Boheman, the cotton boll weevil, consist almost entirely of tw o vitellin types with M(r)s of 160,000 and 47,000. We sequenced their N-terminal ends and one internal cyanogen bromide fragment of the larg e vitellin and compared these sequences with the deduced amino acid se quence from the vitellogenin gene. The results suggest that both the b oll weevil vitellin proteins are products of the proteolytic cleavage of a single precursor protein. The smaller 47,000 M(r) vitellin protei n is derived from the N-terminal portion of the precursor adjacent to an 18 amino acid signal peptide. The cleavage site between the large a nd small vitellins at amino acid 362 is adjacent to a pentapeptide seq uence containing two pairs of arginine residues. Comparison of the bol l weevil sequences with limited known sequences from the single 180,00 0 M(r) honey bee protein show that the honey bee vitellin N-terminal e xhibits sequence homology to the N-terminal of the 47,000 M(r) boll we evil vitellin. Treatment of the vitellins with an N-glycosidase result s in a decrease in molecular weight of both proteins, from 47,000 to 3 9,000 and from 160,000 to 145,000, indicating that about 10-15% of the molecular weight of each vitellin consists of N-linked carbohydrate. The molecular weight of the deglycosylated large vitellin is smaller t han that predicted from the gene sequence, indicating possible further proteolytic processing at the C-terminal of that protein. (C) 1993 Wi ley-Liss, Inc.