FIG. 1.

Configuration and atomic parameters of the major repeating fragment of the S. aureus cell wall. Key points are marked with capital letters A, B, C, and D. Distances in a relaxed conformation are as follows: |AB| = 1.39 nm (stalk peptide), |BC| = 0.61 nm (short arm), |BD| = 2.42 nm (long arm); average disaccharide diameter, 1.1 nm; disaccharide length, 1.0 nm. (a) Tertiary structure of the disaccharide-peptide repeating unit. Bond order and hydrogen atoms are not shown. It is noteworthy that the simulation orients the arms of the peptide antenna perpendicularly to the axis of the disaccharide moiety. The atomic coordinates for this figure in PCModel format can be retrieved from the MONOUNIT.PCM file in the supplemental material. The software for interpreting this file is PCModel, version 7.00 (Serena Software). (b) Schematic representation of the disaccharide-peptide repeating unit, drawn to scale. Gray and white rectangles, GlcpNAc and MurpNAc residues, respectively. The black antenna represents the peptide side chain. The round arrow indicates that the antenna can rotate around the AB axis.