Download MendeleyA structural model for (GlcNAc) 2 translocation via a periplasmic chitooligosaccharide-binding protein from marine Vibrio bacteria.
Kitaoku, Y., Fukamizo, T., Kumsaoad, S., Ubonbal, P., Robinson, R.C., Suginta, W.(2021) J Biol Chem 297: 101071-101071
- PubMed: 34400168
- DOI: https://doi.org/10.1016/j.jbc.2021.101071
- Primary Citation of Related Structures:
6LZQ, 6LZT, 6LZU, 6LZV, 6LZW, 7EBI, 7EBM - PubMed Abstract:
VhCBP is a periplasmic chitooligosaccharide-binding protein mainly responsible for translocation of the chitooligosaccharide (GlcNAc) 2 across the double membranes of marine bacteria. However, structural and thermodynamic understanding of the sugar-binding/-release processes of VhCBP is relatively less. VhCBP displayed the greatest affinity toward (GlcNAc) 2 , with lower affinity for longer-chain chitooligosaccharides [(GlcNAc) 3-4 ]. (GlcNAc) 4 partially occupied the closed sugar-binding groove, with two reducing-end GlcNAc units extending beyond the sugar-binding groove and barely characterized by weak electron density. Mutation of three conserved residues (Trp 363 , Asp 365 , and Trp 513 ) to Ala resulted in drastic decreases in the binding affinity toward the preferred substrate (GlcNAc) 2 , indicating their significant contributions to sugar binding. The structure of the W513A-(GlcNAc) 2 complex in a 'half-open' conformation unveiled the intermediary step of the (GlcNAc) 2 translocation from the soluble CBP in the periplasm to the inner membrane-transporting components. Isothermal calorimetry data suggested that VhCBP adopts the high-affinity conformation to bind (GlcNAc) 2 , while its low-affinity conformation facilitated sugar release. Thus, chitooligosaccharide translocation, conferred by periplasmic VhCBP, is a crucial step in the chitin catabolic pathway, allowing Vibrio bacteria to thrive in oceans where chitin is their major source of nutrients.
Organizational Affiliation:
School of Biomolecular Science and Engineering (BSE), Vidyasirimedhi Institute of Science and Technology (VISTEC), Rayong, Thailand.
