Secretory Polypeptides Encoded in Balbiani Ring Genes

The goal of this project is to learn the structure and assembly characteristics of a family of secretory proteins (SP's). SP's are synthesized in salivary glands of aquatic larvae of the midge, Chironomus. Larvae construct underwater tubes for filter feeding and pupation using silk fibers composed of SP's. During the past year we made progress in two areas. (1) A 1-kb cDNA clone was sequenced that represents a portion of a 4.8-kb poly(A) + RNA. Though it lacks sequences found in other SP mRNA's, its abundance in salivary glands is equal to other SP mRNA's. Antipeptide antibodies are being raised to identify the protein encoded by this mRNA. (2) Infrared and circular dichroism spectrometry have been used to study the structure of synthetic peptides representing the alternating 'constant' and 'subrepeat' domains of SP's. These 1000-kDal proteins appear to consist of alternating domains of alpha- and POLY(Gly)II-helices. (KT)