Figure 3: The 1LysM module and its interaction with carbohydrates.
From: Molecular basis for bacterial peptidoglycan recognition by LysM domains
(a) NMR structure of 1LysM. β-Sheets are residues T4-V8 and G42-V47; α-helices are residues L14-Y21 and V25-N32. (b) 15N HSQC NMR spectra of 1LysM, free (blue) and saturated with 44 equivalents of GlcNAc6 (red). Residues showing significant chemical shift changes are indicated by arrows, and residues broadened and not reappearing by the end of the titration are circled. (c) Summary of chemical shift changes observed for the titration of 1LysM with peptidoglycan (blue), octasaccharide (GlcNAc-MurNAc)4 (red) and GlcNAc6 (yellow). Results for GlcNAc5 and GlcNAc4 are very similar to those for GlcNAc6, whereas tetrasaccharide (GlcNAc-MurNAc)2 is similar to octasaccharide. The sugar backbone is glucosamine for all three oligosaccharides, but in octasaccharide and peptidoglycan alternate sugars are N-acetyl muramic acid (that is, bearing a lactate group at O3′), while in peptidoglycan most N-acetyl muramic acids also carry a peptide stem. Thus, effects of the lactate are seen as differences between GlcNAc6 and the other two, whereas effects of the peptide stem are seen as differences between peptidoglycan and the other two. Residues broadened in the titrations and not observed by the end of the titration are shown as bars with a normalized shift change of 100. Residues are not shown for which any shift change is smaller than the mean. (d) Representation of the data shown in c. Residues broadened beyond detection are in red, residue T13 implicated in binding the N-acetyl muramic acid lactate group is in magenta and residues implicated in binding peptide stems are in yellow.
