title: A novel giant secretion polypeptide in Chironomus salivary glands: implications for another Balbiani ring gene.
abstract: Chironomus salivary glands contain a family of high Mr (approximately 1,000 X 10(3)) secretion polypeptides thought to consist of three components: sp-Ia, sp-Ib, and sp-Ic. The use of a new extraction protocol revealed a novel high Mr component, sp-Id. Results of a survey of individual salivary glands indicated that sp-Id was widespread in more than a dozen strains of C. tentans and C. pallidivittatus. Sp-Id was phosphorylated at Ser residues, and a comparison of cyanogen bromide and tryptic peptide maps of 32P-labeled polypeptides suggested that sp-Ia, sp-Ib, and sp-Id are comprised of similar but nonidentical tandemly repeated amino acid sequences. We concluded that sp-Id is encoded by an mRNA whose size and nucleotide sequence organization are similar to Balbiani ring (BR) mRNAs that code for the other sp-I components. Furthermore, parallel repression of sp-Ib and sp-Id synthesis by galactose led us to hypothesize that both of their genes exist within Balbiani ring 2.
mesh_terms: D000818:Animals; D002683:Chironomidae; D002875:Chromosomes / Q000648:ultrastructure; D004591:Electrophoresis, Polyacrylamide Gel; D005690:Galactose / Q000494:pharmacology; D005796:Genes; D019476:Insect Proteins; D010446:Peptide Fragments / Q000032:analysis; D010750:Phosphoproteins / Q000032:analysis; D010768:Phosphoserine / Q000032:analysis; D012469:Salivary Glands / Q000032:analysis; D012471:Salivary Proteins and Peptides / Q000235:genetics / Q000302:isolation & purification*; D013045:Species Specificity
chemical_list: D019476:Insect Proteins; D010446:Peptide Fragments; D010750:Phosphoproteins; D012471:Salivary Proteins and Peptides; D010768:Phosphoserine; D005690:Galactose