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Cooperative binding of LysM domains determines the carbohydrate affinity of a bacterial endopeptidase protein

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Cellulose, chitin and peptidoglycan are major long chain carbohydrates in living organisms and comprise a substantial fraction of the biomass. Characterization of the biochemical basis of dynamic changes and degradation of these β,1-4 linked carbohydrates is therefore important for both functional studies of biological polymers and for biotechnology. Here, we investigate the functional role of multiplicity of the carbohydrate-binding LysM domain that is found in proteins involved in bacterial peptidoglycan synthesis and remodelling. The B. subtilis peptidoglycan hydrolysing NlpC/P60 D,L-endopeptidase, CwlS, possesses four LysM domains. The contribution of each LysM domain is determined by direct carbohydrate binding studies in aqueous solution using Microscale Thermophoresis. We show that bacterial LysM domains have affinity for N-acetylglucosamine polymers (GlcNac) in the lower μM range. Moreover, we demonstrate that a single LysM domain is able to bind carbohydrate ligands and that LysM domains act additively to increase the binding-affinity. Our study reveals that affinity for GlcNac polymers correlates to the chain length of the carbohydrate and suggests that binding of long carbohydrates is mediated by LysM domain cooperativity. We also show that bacterial LysM domains, contrary to plant LysM domains do not discriminate between GlcNac polymers and recognize both PGN fragments and chitin polymers with similar affinity. Finally, an alanine replacement study suggests that the carbohydrate-binding site in LysM containing protein is conserved throughout phyla. This article is protected by copyright. All rights reserved.
Original languageEnglish
JournalF E B S Journal
Pages (from-to)1196-1208
Number of pages13
Publication statusPublished - Feb 2014

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