Proton NMR Studies of Co(II) Complexes of the Peptide Antibiotic Bacitracin and Analogues
—Insight into Structure-Activity Relationship
Biochemistry 2000, 39, 4037–4045. (abstract 23)

Jon D. Epperson and Li-June Ming*
Department of Chemistry and
Institute for Biomolecular Science
University of South Florida
Tampa, Florida 33620-5250

Stereoview of Co(II)-bacitracin A1 structure produced by the use of the Cerius2 molecular modeling program.  Distance constrains were obtained from the T1 values of the assigned isotropically shifted proton NMR signals of the complex in H2O at pH 5.5.  The structural model indicates that the N-terminus (Ile-1 to Glu-4) of bacitracin wraps around the Co(II) ion with only the His-10 imidazole ring bridging the cyclic heptapeptide to the Co(II) ion.  The Phe-9 and the Ile-5 side chains are in close proximity and may serve as a flexible hydrophobic binding site for lipid pyrophosphates.