Insect vitellins: Identification of primary products of translation

Abstract The primary products of translation of the vitellins of Hyalophora cecropia, Tenebrio molitor , and Aedes aegypti were identified by pulse‐chase labeling in fat body incubated in vitro, specific antisera being used to identify the immunospecific products. The vitellogenin of H. cecropia was found to be synthesized as a polypeptide of 220,000 daltons (220 K), which was cleaved to yield two polypeptides of 180 K and 47 K. The immunoprecipitable polypeptides secreted into the media during a 3‐hour culture were also 180 K and 47 K. The vitellogenin of T. molitor was synthesized as 204 K primary translation products, which were cleaved to yield polypeptides of 160 K, 56 K, and 45 K. A. aegypti vitellogenin differed from those H. cecropia and T. molitor in that the protein was synthesized as two closely migrating polypeptides of about 170 K, which were not cleaved prior to secretion. RNA from blood‐fed female A. aegypti directed the synthesis of polypeptides, in the rabbit reticulocyte cell‐free protein synthesizing system, which were of similar weight to the vitellin polypeptides. These results, taken together with data published elsewhere on certain higher Diptera, support the division of insect vitellins into three broad structural groups, as already proposed (Harnish and White, 1982).