Biosynthesis of gramicidin S. II. Incorporation experiments with labeled amino acid analogs, and the amino acid activation process

Biosynthesis of gramicidin and tryocidine in the Dubos strain of Bacillus brevis. I. Experiments with growing cultures

Okuda, Kiyoshi (Department of Biochemistry and Biophysics, University of Hawaii, Honolulu), Gordon C. Edwards, and Theodore Winnick. Biosynthesis of gramicidin and tyrocidine in the Dubos strain of Bacillus brevis. I. Experiments with growing cultures. J. Bacteriol. 85:329-338. 1963.-A simple chromatographic method was developed for the isolation of gramicidin and tyrocidine from tyrothricin of Bacillus brevis. A Tryptone-yeast extract-glucose medium containing mineral salts gave the best yields of peptides in a stationary culture of the organism. The incorporation of suitable C(14)-labeled amino acids into gramicidin and tyrocidine was studied Several analogues of tyrocidine amino acids (beta-hydroxyglutamic acid, pipecolic acid, beta-2-thienylalanine, p-fluorophenylalanine, and phenyl glycine) selectively reduced tyrocidine synthesis, when added to the nutrient medium. At the same time, the production of gramicidin was augmented. Growth and protein synthesis were not affected. Two analogues in isotopic form, beta-2-thienylalanine and isoleucine, were shown to give rise to high degrees of labeling in tyrocidine.

THE BIOSYNTHESIS OF GRAMICIDIN S IN A CELL-FREE SYSTEM

1. A cell-free system prepared from Bacillus brevis cells, harvested in the late phase of growth and consisting of the 11000g supernatant, has been shown to incorporate into gramicidin S the five constituent amino acids added in labelled form. The results are consistent with complete synthesis and not merely a completion of pre-existing intermediate peptides. 2. The incorporation of (14)C-labelled amino acids by the 11000g supernatant into gramicidin S requires an energy source. Omission of phosphoenolpyruvate and pyruvate kinase from the incubation mixture prevents incorporation into gramicidin S. The cell-free system incorporates [(14)C]-leucine, -proline and -phenylalanine over a period of 4hr. With [(14)C]leucine, incorporation into gramicidin S takes place in the range pH6-9 with maximum incorporation at pH7.0. High concentrations of chloramphenicol or puromycin decreased the incorporation into gramicidin S by only about 20%. 3. The 50000g supernatant exhibited no decrease in ability of incorporating [(14)C]valine into gramicidin S as compared with the 11000g supernatant. About 40% of the incorporating ability remained in the 105000g supernatant after 3hr. centrifugation. When recombining the 105000g sediment with the 105000g supernatant, some increase in incorporation over that obtained with the supernatant alone was obtained. The findings tend to support the view that gramicidin S is synthesized in a different manner from that of proteins.