PURIFICATION AND CHARACTERIZATION OF VITELLOGENIN FROM THE GYPSY-MOTH, LYMANTRIA-DISPAR

Vitellogenin (Vg), the precursor of vitellin (Vt), an abundant egg yolk protein, was purified from the hemolymph of the gypsy moth (Lymantria dispar) using FPLC techniques. The purified protein gave a single band in native polyacrylamide gel electrophoretic analysis corresponding to a size of approximately 487 kDa. It consisted of three types of subunits of 190, 165 and 36 kDa (Vg190, Vg165 and Vg36, respectively). Sodium dodecyl sulfate PAGE analysis of egg extracts showed the presence of three proteins having sizes identical to those of Vg subunits (Vt190, Vt165 and Vt36, respectively). The larger Vg subunits were found to share sequence homology by western blot analysis, peptide mapping, amino acid composition and N-terminal sequencing. The change in the proportion of these subunits observed during development suggested that Vg165 might be derived from Vg190. The N-terminal sequences of Vt165 and Vt36 were identical to their respective counterparts in Vg. This indicates that processing of Vg into Vt does not involve proteolytic cleavage at the N-termini of the subunits.