On the Heterogeneity of Gramicidin

Gramicidin. VII. The Structure of Valine- and Isoleucine-gramicidin B

“…4 The configuration of 7-hydroxy-L-lysine is of interest for the mechanism of the photochlorination and for the related 7-hydroxyhomoarginine, a new natural amino acid of unknown configuration recently isolated from Lathyrus species. 5,6 In this investigation the configuration of 7-hydroxylysine is shown to be threo. It is assumed that 7-chlorolysÍne has the erythro configuration and that its conversion to hydroxylysine involves 100% inversion.…”

“…By countercurrent distribution in the solvent system methanol-waterbenzene-chloroform (23:7:15:15) three fractions were obtained, the major fraction designated gramicidin A (distribution coefficient K = 0.61), and two minor fractions designated gramicidin B (K = 0.31) and gramicidin C (K = 1.32). [3][4][5] The structure of gramicidin A, a mixture of valine-(I) and isoleucine-gramicidin A (II),5'6 was recently elucidated7-9 and confirmed by synthesis. 10 Gramicidin B is composed of very similar acids except that one tryptophan is replaced by phenylalanine.…”

“…Chem., 235, 2031(1960. (18) J. P. Greenstein, S. M. Birnbaum, and M. C. Otey, ibid.,204, 307 (1953).2028Journal of the American Chemical Society / 87:9 / May5, 1965…”

NMR solution structure of gramicidin A complex with caesium cations

“…GA was obtained from gramicrdm D (Serva) by countercurrent distribution [22]. The sample used for NMR studies also contained 4-5% of [Ile']gramictdm A as determmed by ammo actd analysis.…”

Gramicidin K, a new linear channel-forming gramicidin from Bacillus brevis

“…The polyenzyme systems produce peptides of defined length, but the sequence fidelity of the process is somewhat lower than for ribosomal protein synthesis, and so some heterogeneity of the products is observed. The linear gramicidins, for example, are heterogeneous at positions 1 (valine or isoleucine) and 11 (tryptophan, phenylalanine, or tyrosine) in the sequence of 15 amino acids (Gregory & Craig, 1948; Ramachandran, 1963;Sarges & Witkop, 1965a-c). This heterogeneity is presumably due to a relaxed enzymatic specificity for the amino acid to be incorporated at each of these positions in the peptide (Lipmann, 1973).…”