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Structure and function of a novel periplasmic chitooligosaccharide-binding protein from marine Vibrio bacteria

DOI: 10.1074/jbc.RA117.001012 DOI Help

Authors: Wipa Suginta (Suranaree University of Technology) , Natchanok Sritho (Suranaree University of Technology) , Araya Ranok (Rajamangala University of Technology Isan) , David Bulmer (Newcastle University) , Yoshihito Kitaoku (Kindai University) , Bert Van Den Berg (Newcastle University) , Tamo Fukamizo (Kinki University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Biological Chemistry

State: Published (Approved)
Published: February 2018

Abstract: Periplasmic solute-binding proteins (SBPs) in bacteria are involved in the active transport of nutrients into the cytoplasm. In marine bacteria of the genus Vibrio, a chitooligosaccharide-binding protein (CBP) is thought to be the major SBP controlling the rate of chitin uptake in these bacteria. However, the molecular mechanism of the CBP involvement in chitin metabolism has not been elucidated. Here, we report the structure and function of a recombinant chitooligosaccharide-binding protein from Vibrio harveyi, namely VhCBP, expressed in Escherichia coli. Isothermal titration calorimetry (ITC) revealed that VhCBP strongly binds shorter chitooligosaccharides [(GlcNAc)n, n = 2, 3, and 4] with affinities that are considerably greater than those for glycoside hydrolase family 18 (GH18) and GH19 chitinases, but does not bind longer ones, including insoluble chitin polysaccharides. We also found that VhCBP comprises two domains with flexible linkers and that the domain–domain interface forms the sugar-binding cleft, which is not long extended but forms a small cavity. (GlcNAc)2 bound to this cavity, apparently triggering a closed conformation of VhCBP. Trp-363 and Trp-513, which stack against the two individual GlcNAc rings, likely make a major contribution to the high affinity of VhCBP for (GlcNAc)2. The strong chitobiose binding, followed by the conformational change of VhCBP, may facilitate its interaction with an active-transport system in the inner membrane of Vibrio species.

Journal Keywords: chitin recycling; sugar-protein interactions; glycoside hydrolase; solute-binding protein; nutrient transport; isothermal titration calorimetry (ITC); prokaryotic signal-transduction; carbohydrate metabolism; structure-function; carbohydrate processing

Subject Areas: Biology and Bio-materials

Instruments: I04-1-Macromolecular Crystallography (fixed wavelength)

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