Cross-link formation and peptidoglycan lattice assembly in the FemA mutant of Staphylococcus aureus

Abstract

Staphylococcus aureus FemA mutant grown in the presence of an alanine-racemase inhibitor was labeled with d-[1-13C]alanine, l-[3-13C]alanine, [2-13C]glycine, and l-[5- 19F]lysine to characterize some details of the peptidoglycan tertiary structure. Rotational-echo double-resonance (REDOR) NMR of isolated cell walls was used to measure internuclear distances between 13C-labeled alanines and 19F-labeled lysine incorporated in the peptidoglycan. The alanyl 13C labels were preselected for REDOR measurement by their proximity to the glycine label using 13C-13C spin diffusion. The observed 13C-13C and 13C- 19F distances are consistent with a tightly packed, hybrid architecture containing both parallel and perpendicular stems in a repeating structural motif within the peptidoglycan. © 2014 American Chemical Society.