Some properties of the bacitracin polypeptides

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Abstract
A sample of crude bacitracin was resolved by counter-current distribution between solvents into at least 10 polypeptides. These were named bacitracins E, D, B, A[image], A, C, G, F1, F2 and F3. Their partition coeffs. (=concn. in alcohol phase/concn. in aqueous phase) at pH 7.0 increase in this order. The u.-v. absorption spectra of the bacitracins fall into 3 groups. Bacitracins E, D, B, and A show broad maxima at 253 m[mu]. Bacitracins C and G absorb more strongly and show a sharp maximum at 250 m[mu] and a shoulder at 268 m[mu]. Bacitracins F1, F2 and F3 all show a shoulder at 253 m[mu] and a broad maximum at 288 m[mu]. All the bacitracins contain cysteine, ornithine, lysine, histidine, aspartic acid, glutamic acid, leucine and/or isoleucine and phenylalanine residues. However, bacitracins B, D and E differ from A in yielding on acid hydrolysis a substance which behaves like valine on paper chromatograms, and bacitracin C differs from A in yielding a substance which behaves like glycine. Smaller amts. of the valine-like substance are obtained from bacitracins G, F1, F2 and F3. The bacitracins contain no free thiol group, but a thiol group appears to be liberated in all of them on mild acid hydrolysis. At the same time ammonia appears to be liberated from an amide group in bacitracins B, A, C, G, F1, F2 and F3, bacitracins E and D containing very little, if any, amide N.
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