Purification and characterization of yolk protein‐2 from the fall webworm,Hyphantria cuneadrury

Abstract

Yolk proteins (YPl, YP2, and YP3) of the fall webworm, Hyphantria cunea, are of relatively low molecular weight. Yolk protein-2 (YP2) was purified from gel slices and by KBr density gradient ultracentrifugation followed by ion exchange chromatography. YP2 i s composed of one subunit with a molecular weight of 35.5 kDa. YP2 contains neutral lipids (diacylglycerol and triacylglycerol) and phospholipids (phosphatidylcholine and phosphatidylethanolamine). The neutral lipids are largely composed of lauric acid and palrnitoleic acid. YP2 contains relatively large amounts of glutamic acid and aspartic acid but small amounts of tyrosine, phenylalanine, and methionine. YP2 is a vitellin (Vn) synthesized by the fat body. Vitellogenin-2 (Vg2), the precursor of YP2, is present in very small amounts in the hemolymph. Lipophorin and storage protein also are found in the ovary of H. cunea, and these proteins do not immunologically cross-react with YP2. YP2 is detected in first instar larvae but completely disappears during the second instar, indicating that YP2 is intensively utilized during postembryonic development. Anti-YP2 antibodies cross-react with ovarial extracts of Bornbyx mori but not with those of insects from other orders such as Cletus schrnidti (Hemiptera), Lucilia illustris (Diptera), Anechura japonica (Dermaptera), Periplaneta americana (Dictyoptera), and Ducetia japonica (Orthoptera). o 1995 WiIey-Liss, Inc.

Fat body expressed yolk protein genes in Hyphantria cunea are related to the YP4 follicular epithelium yolk protein subunit gene of pyralid moths

“…The three major yolk proteins of H. cunea , YP1, YP2 and YP3, are small proteins of molecular masses between 18 and 32.2 kDa (Lee et al ., 1995). We isolated the YP1 and YP2 cDNA clones containing inserts of 1.2 kb and 1.1 kb, respectively.…”

“…Ovaries accumulated several peptides, three of which were identified as YP1, YP2 and YP3, based on their relative mobilities in native and denaturing SDS/PAGE (Han & Kim, 1986; Lee et al ., 1995). SDS/PAGE (Fig.…”

“…This suggests that the two YPs may have arisen by a recent gene duplication. However, even though the two proteins share such a high level of similarity in amino acid sequence, they do not associate to form a heteromeric protein (Lee, 1993; Lee et al ., 1995). The divergence in their sequences must have led to significant structural changes that do not allow the two proteins to bind with each other.…”

“…YP1 and YP2 were purified from the adult ovaries using KBr ultracentrifugation and DEAE according to Lee et al . (1995).…”

“…These three yolk proteins are found in both the haemolymph and ovaries of late pupae and adults, and together they constitute 40% of total egg protein (Han & Kim, 1986). Both YP1 and YP2 appear in yolk spheres after the onset of patency during vitellogenesis and can be detected until egg hatch (Lee et al ., 1995; Cheon et al ., 2001), demonstrating their utilization during embryogenesis. On the other hand, while YP3 accumulates in the yolk sphere concomitantly with YP1 and YP2, it persists through the 2nd instar (data not shown).…”