Behaviour of the tRNA population during the process of fibroin synthesis in Bombyx mori

The behaviour of Bombyx mori tRNA isoaccepting species specific for glycine alanine and methionine, obtained from the posterior silkgland during different developmental stages has been studied by fractionation of tRNA on B. D. cellulose column chromatography. Specific quantitative changes were observed in isoacceptors tRNA species for glycine and alanine the two major amino acid constituents of silk fibroin. Although methionine is not part of the silk-fibroin molecule, one tRNA(Met) isospecie, which has properties consistent with its involvement in the initiation of protein synthesis was detected in significant amounts at the stage in which the posterior silkgland synthesizes exclusively fibroin protein. Thus the quantitative changes in specific tRNA species are clearly associated with the changes in protein synthesis which occur during terminal differentiation of the silkgland.