The N-terminal and sulphur-containing residues of bacitracin A

Experiments on the lysine and aspartic acid residues in bacitracin A

“…Desulphurized bacitracin. This was prepared by treating commercial bacitracin with Raney nickel as described by Lockhart et al (1955).…”

“…Experiments on the Lysine and Aspartic Acid Residues in Bacitracin A BY I. M. LOCKHART AND E. P. ABRAHAM Sir William Dunn School of Pathology, University of Oxford (Received 19 September 1955) In several structural features the bacitracin family appears to be unique among polypeptides that have so far been subjected to detailed chemical study. The N-terminal and sulphur-containing residues in bacitracin A have been discussed in an earlier paper (Lockhart, Abraham & Newton, 1955). In addition to this portion of the molecule, the lysine residue is a centre of interest.…”

Total Structures and Antimicrobial Activity of Bacitracin Minor Components.

“…The components of 6,7,10,ll,12,13,15 and 16,andpeaksNo. 24,25,26,27,28,29 and 31 Comparison of the MICsand the proposed structures of the minor componentssuggest that the location of the valine affects the activity of each component in the following decreasing order: TV-terminus, the seven membered peptide ring, and the side chain peptide moiety. Because this order is related to the elution order of the minor components on the HPLC, the activity may depend on the hydrophobicity of the respective component.…”

“…7,10,ll,12,13,15,16,24,25,26,27,28,29and 31 as indicated in Fig. 1 Table 1 were considered to be all D-alloisoleucines derived from TV-terminal L -isoleucines.…”

Problems Relating to the Biosynthesis of Peptide Antibiotics

“…Moreover, in long-term experiments D-valine inhibited total antibiotic synthesis by this organism without inhibiting cell growth 51 and also inhibited the incorporation of 1-14 C-L-valine into the antibiotic. However, the penicillins may represent a special case, since it is a plausible hypothesis that their thiazolidine ring is formed by the addition of the thiol group of a cysteine residue to the double bond of a residue of 2,3-dehydrovaline, and this could result in the formation of a D centre, irrespective of the configuration of the original valine precursor (VIII) 54 residues play a wider role in the formation of D centres in peptide antibiotics is not known, but a residue of dehydrotryptophan has been found to occur in telomycin 16 , and racemisation in the N-terminal isoleucine residue of bacitracin appears to be facilitated by resonance 56 (see next page). 1-14 C-L-Valine was found to be incorporated much more efficiently into benzylpenicillin than D-valine, even though the uptake of the D-isomer was not very much less than that of the L-isomer 53 .…”