Vitellogenin of the cicada Graptopsaltria nigrofuscata (Homoptera): analysis of its primary structure.

We cloned and sequenced the cDNA of vitellogenin (Vg) from the cicada Graptopsaltria nigrofuscata (Homoptera). The deduced amino acid sequence of 1987 residues (including 16 residues for a putative signal peptide) was obtained. The pro-Vg was cleaved into two subunits between residues 379 and 380 following a consensus RXXR cleavage site sequence, secreted as S-Vg (apparent molecular weight 43 kDa) and L-Vg (200 kDa), sequestered, and stored in the egg as two vitellins (Vns), S-Vn and L-Vn, with similar respective molecular weights. There was a single long serine-rich stretch closely following the cleavage site. The entire amino acid sequences of the Vgs from the eight insects so far reported could be aligned confidently. The presence of subdomains I-V (areas of relatively high amino acid conservation) and of 10 cysteines at conserved locations at the C-terminus, noted previously among insect Vgs, were confirmed. Antisera raised against G. nigrofuscata S- and L-Vn cross-reacted with the S- and L-Vg/Vn, respectively, of all three other cicada species examined. Another major egg protein (170 kDa) unrelated to Vg/Vn, was also detected in all species examined.