FIG 3.

Impact of lipid II amidation on the inhibitory effect of different glycopeptide antibiotics in vitro. Purified lipid II or amidated lipid II (d-isoglutamine instead of d-glutamate in position 2 of the stem peptide) was used as a substrate in a FemX in vitro assay (see Materials und Methods). The addition of [¹⁴C]glycine to the lipid precursor in the absence and presence of vancomycin, chloroeremomycin, or oritavancin was quantified using a Storm PhosphorImager. Antibiotics were added in equimolar ratio (1:1) with respect to the lipid precursor. The mean values from three independent experiments are shown. All experiments were performed at least in triplicate, and data are presented as means ± standard deviations (SD). VAN, vancomycin; CEM, chloroeremomycin; ORI, oritavancin.