Vancomycin Derivative with Damaged d-Ala-d-Ala Binding Cleft Binds to Cross-linked Peptidoglycan in the Cell Wall of Staphylococcus aureus

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Abstract
Des-N-methylleucyl-4-(4-fluorophenyl)benzyl-vancomycin (DFPBV) retains activity against vancomycin-resistant pathogens despite its damaged d-Ala-d-Ala binding cleft. Using solid-state nuclear magnetic resonance (NMR), a DFPBV binding site in the cell walls of whole cells of Staphylococcus aureus has been identified. The cell walls were labeled with d-[1-13C]alanine, [1-13C]glycine, and l-[ϵ-15N]lysine. Internuclear distances from 19F of the DFPBV to the 13C and 15N labels of the cell-wall peptidoglycan were determined by rotational-echo double-resonance (REDOR) NMR. The 13C{19F} and 15N{19F} REDOR spectra show that, in situ, DFPBV binds to the peptidoglycan as a monomer with its vancosamine hydrophobic side chain positioned near a pentaglycyl bridge. This result suggests that the antimicrobial activity of other vancosamine-modified glycopeptides depends upon both d-Ala-d-Ala stem-terminus recognition (primary binding site) and stem-bridge recognition (secondary binding site).