Studies on the complex formed between bacitracin A and divalent cations

Duane A. Scogin, Thomas O. Baldwin, Robert B. Gennis

Research output: Contribution to journalArticlepeer-review


Bacitracin A is a peptide antbiotic which forms stoichiometric complexes with divalent cations, including Ni2+ and Zn2+. In this paper it is shown that the metal-bacitracin complex contains a group which has a pKa near pH 5.5. Deprotonation of the group is concomitant with the aggregation and precipitation of the metal-bacitracin complex. Bacitracin A, in the absence of metals, does not contain any group which has a pKa in this range. It is postulated that this group is the N-terminal amino of isoleucine, which was previously postulated not to be directly involved in metal coordination based on proton release measurements. An attempt was made to demonstrate directly that the N-terminal amino group is not coordinated to the metal by examining the reactivity of this group with 2,4,6-trinitrobenzene sulfonate. It was clearly shown that bound metals protect the N-terminal amino group from reacting with this reagent. It is speculated that this metal-protection results from a combination of factors, including steric hindrance.

Original languageEnglish (US)
Pages (from-to)184-188
Number of pages5
JournalBiochimica et Biophysica Acta (BBA)/Protein Structure and Molecular
Issue number1
StatePublished - Jan 12 1983


  • Bacitracin A
  • Divalent cation
  • Metal binding

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology


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