Analysis of mosquito vitellogenin cDNA. Similarity with vertebrate phosvitins and arthropod serum proteins

Abstract

The cDNA coding for vitellogenin of the mosquito Aedes aegypti was cloned and sequenced. An immunological analysis of expressed deletions from the 5'-end of the vitellogenin cDNA clones using vitellogenin subunit-specific antibodies showed that the small vitellogenin subunit is located at the N terminus and the large one at the carboxy-portion of the pre-provitellogenin. The position of the cleavage between the vitellogenin subunits in the pre-provitellogenin was identified by locating the N terminus of the large subunit. The cleavage site has a consensus RXRR for the subtilisin-processing endoprotease. Mosquito vitellogenin is highly hydrophilic with 17 putative N-linked glycosylation sites and 13 potential tyrosine sulfation sites. In contrast to known invertebrate vitellogenins, mosquito vitellogenin contains three polyserine domains that are similar to those of phosvitins in vertebrate vitellogenins. These polyserine domains, originally presumed to be vertebrate-specific, have several phosphorylation consensus sites in their sequences. Unlike other known vitellogenins, mosquito vitellogenin is rich in aromatic amino acid residues, tyrosine and phenylalanine, and in this respect is similar to insect serum proteins, arylphorins. This similarity suggests that mosquito vitellogenin may supply aromatic amino acids to the cuticle of rapidly developing embryos.