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Figure 8
Structural differences between N-acetylglucos­aminidases and muramid­ases (lysozymes) in binding glycan cell-wall components. Images of three-dimensional models were prepared with MAIN (Turk, 2013BB48) and rendered with Raster3D (Merritt & Bacon, 1997BB36). (a) and (c) show a schematic representation of the approach of N-acetylglucosaminidases (a) and muramid­ases (c) to the poly-NAG-NAM saccharide, where the lactyl moieties are oriented towards the L- and R-lobes, which correspond to glucosaminidase and muramid­ase binding, respectively. (b) and (d) are models of the hexasaccharide (NAG-NAM)3 bound to the AtlE and ACOD active sites, shown in ball-and-stick representation against the surface of the targeted enzyme. The atom colour codes of the hexasaccharide model are blue and red for N and O atoms, respectively. C atoms are coloured orange, except for those from the lactyl group, which indicate the site of peptide-chain attachment; these are coloured green. The surface is white, except for the part corresponding to the carboxylic group of the catalytic residue Glu138, which is coloured red. The chain trace of ACOD is shown in blue against the surface of AtlE (b), whereas the chain trace of AtlE is shown in cyan against the surface of ACOD (d). (e) Cleavage sites of muramidases and N-acetylglucosaminidases. The three-dimensional model of the NAG-NAM-NAG-NAM tetrasaccharide is shown in ball-and-stick representation using the same colour codes as in (b) and (d). The cleavage sites of muramidases and N-acetylglucosaminidases are marked with arrows.

Volume 4| Part 2| March 2017| Pages 185-198
ISSN: 2052-2525