Glycine gramicidin

Gordon, Martin and Synge18 utilized their new and elegant technique, chromatography, to establish the amino acid composition of gramicidin. They proposed a 24 unit cyclic peptide consisting of six moles each of leucine, and tryptophane, 5 moles of valine, 3 moles of alanine and 2 moles each of glycine and unknown hydroxyamino compound. 

Tokito K, Hori K, Kurotsu T, Kanda M, Saito Y. Effect of single base substitution at glycine-870 codon of gramicidin S synthetase 2 gene on pioline activation. J Biochem 1993 ... 

Saito M, Hori K, Kurotsu T, Kanda M, Saiio Y. Three conserved glycine residues in valine activation of gramicidin 5 synthetase 2 from BociUtis breu s. J Biochem 1994 117 276-282. Tokita K, Hori K, Kurotsu T Kanda M. Saito Y. Effect of single base substitutions at glycine-870 codon of gramicidin S synthetase 2 gene on proline activation. ] Biochem 1993 114 522-527. 

Ala = alanine DMPC = dimyristoyl phosphatidylcholine GA = gramicidin A Gly = glycine Leu = leucine Phe = phenylalanine PRC = photosynthetic reaction center SDS = sodium dodecyl sulfate Trp = tryptophan Tyr = tyrosine Val = valine. 

The lability of tryptophan under the conditions usually employed for acid hydrolysis of proteins (6N HCl, 24 hrs, in sealed tubes under vacuum) is not due to instability of the indole nucleus under such conditions, but to side reactions involving non-proteinaceus material, like carbohydrates, or to the presence of particular amino acids in the acidic hydrolysis mixture. In fact, gramicidin A, a pentadecapeptide containing, apart from tryptophan, only purely aliphatic amino acids like glycine, alanine, leucine and valine, gives a quantitative recovery of tryptophan after acid hydrolysis in 6N HCl (l20). 

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