FIGURE 2.
Elimination of the terminal D-ala residue has strong influence on the 3D structure of PG subunits. PG monomeric subunits derived from the M5 by elimination of the terminal D-ala (M4) or the terminal D-ala-D-ala (M3) are compared in two orientations, transversal to (upper panel) and from above (lower panel) the surface of the sacculus. To facilitate comparison muropeptides were rotated until GlcNAc residues overlap. Red designates the glycan moiety and blue the stem peptide. Terminal D-ala residues are highlighted in yellow. The 3D structures were calculates as in Figure 1. Hydrogen atoms were removed in the image, but considered for the calculation of the molecular surface.