Figure 2: Identification of the structural motif recognized by LysM. Red rectangle is GlcNAc, pink rectangle is MurNAc, blue circles are peptide stem with (darker blue) crosslinking peptides.
From: Molecular basis for bacterial peptidoglycan recognition by LysM domains
The six LysM module polypeptide (L1–L6) was immobilized on a CM5 chip and binding was measured with surface plasmon resonance (SPR) using analyte mixtures corresponding to soluble Staphylococcus aureus peptidoglycan fragments generated using three enzymes with distinct cleavage specificities: (a) amidase digest, containing a mixture of peptide stems and glycan chains; (b) endopeptidase digest, containing linear (non cross-linked) peptidoglycan; (c) muramidase digest, containing disaccharides linked to peptide stems, some of which are cross-linked; (d) synthetic peptide stems. RU, resonance units (e) Affinity purification of AtlA L1–L6 LysM domain and cytochrome c with insoluble polysaccharides: 1, peptidoglycan; 2, chitin; 3, cellulose; 4, xylan. Protein remaining in the supernatant (Unbound) and associated with the pellet (Bound) were analysed by SDS–PAGE and Coomassie staining. Cytochrome c was used as a control, as this protein displays a similar isoelectric point to the LysM domain (pI=9.6 versus 10.06, respectively). No binding activity was detected with cytochrome c using any of the polysaccharides.
