<i>Staphylococcus aureus</i> Peptidoglycan Stem Packing by Rotational-Echo Double Resonance NMR Spectroscopy

Abstract

<i>Staphylococcus aureus</i> grown in the presence of an alanine-racemase inhibitor was labeled with d-[1-¹³C]­alanine and l-[¹⁵N]­alanine to characterize some details of the peptidoglycan tertiary structure. Rotational-echo double-resonance NMR of intact whole cells was used to measure internuclear distances between ¹³C and ¹⁵N of labeled amino acids incorporated in the peptidoglycan, and from those labels to ¹⁹F of a glycopeptide drug specifically bound to the peptidoglycan. The observed ¹³C–¹⁵N average distance of 4.1–4.4 Å between d- and l-alanines in nearest-neighbor peptide stems is consistent with a local, tightly packed, parallel-stem architecture for a repeating structural motif within the peptidoglycan of <i>S. aureus</i>