Gramicidin B

Gramicidin B is part of the collective Gramicidin D that is an antibiotic obtained from a soil microbe- Bacillus brevis. This antibiotic forms channels in the cell membrane through which cations inside the cell begin to leave, thus disrupting the ion potential and eventually killing the cell. Gramicidin B makes up 6% of Gramicidin D while Gramicidin A and C make up 80% and 14% respectively. Gramicidin D is a linear pentadecapeptide made up of 15 amino acids. The 11th amino acid in these chains leads to the three different types of gramicidins. Gramicindin A contains tryptophan in the 11th position while B and C have phenylalanine and tyrosine respectively.