The secretion proteins in Chironomus tentans salivary glands: Electrophoretic characterization and molecular weight...

A new method for isolating the secretion products fromChironomus tentans salivary glands is described. This method has the advantage of allowing the isolation of soluble and undegraded secretion proteins. These proteins have been characterized on SDS-acrylamide gels. Three main proteins (SPI, SPII, and SPIII), with molecular weights of about 1.4, 1.0 and 0.16×10⁶ D were detected. The number of major bands is that expected if, as has been suggested, the three Balbiani rings on the fourth chromosome contain the genes for the secretion proteins. Moreover, the molecular weights of SPI and SPII are in the range expected from the size of Balbiani ring transcripts. In addition we present evidence for a protease which is isolated with the secretion proteins and is fully active only in the presence of reducing agents. This result suggests that a secondary structure, maintained by disulfide bonds, is necessary to prevent proteolytic cleavage of secretion proteins.