부산대학교 도서관

Cellulose, chitin and peptidoglycan are major long-chain carbohydrates in living organisms, and constitute 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 biotechnology. Here, we investigated the functional role of multiplicity of the carbohydrate-binding lysin motif ( Lys M) domain that is found in proteins involved in bacterial peptidoglycan synthesis and remodelling. The Bacillus subtilis peptidoglycan-hydrolysing Nlp C/ P60 d, l-endopeptidase, cell wall-lytic enzyme associated with cell separation, possesses four Lys M domains. The contribution of each Lys M domain was determined by direct carbohydrate-binding studies in aqueous solution with microscale thermophoresis. We found that bacterial Lys M domains have affinity for N-acetylglucosamine (GlcNac) polymers in the lower-micromolar range. Moreover, we demonstrated that a single Lys M domain is able to bind carbohydrate ligands, and that Lys M domains act additively to increase the binding affinity. Our study reveals that affinity for Glc NAc polymers correlates with the chain length of the carbohydrate, and suggests that binding of long carbohydrates is mediated by Lys M domain cooperativity. We also show that bacterial Lys M domains, in contrast to plant Lys M domains, do not discriminate between Glc NAc polymers, and recognize both peptidoglycan fragments and chitin polymers with similar affinity. Finally, an Ala replacement study suggested that the carbohydrate-binding site in Lys M-containing proteins is conserved across phyla. [ABSTRACT FROM AUTHOR]