22HI

Beta-1,2-glucan-binding protein complexed with cyclic beta-1,2-glucoheptadecaose

Summary for 22HI

• Entry DOI: 10.2210/pdb22hi/pdb
• Descriptor: Extracellular solute-binding protein family 1, Cycloheptadecakis-(1-2)-(beta-D-glucopyranose), GLYCEROL, ... (4 entities in total)
• Functional Keywords: carbohydrate-binding protein, sugar binding protein
• Biological source: Chloroflexus aurantiacus Y-400-fl
• Total number of polymer chains: 1
• Total formula weight: 55919.78

Authors

Hirayama, R.,Nakajima, M. (deposition date: 2026-01-11, release date: 2026-05-27)

Primary citation

Kato, K.,Kaneko, T.,Hirayama, R.,Tanaka, N.,Nakai, H.,Torigoe, H.,Nakajima, M.
Structural and thermodynamic analyses of a novel beta-1,2-glucan binding mode in the ABC transporter solute-binding protein Chy400_4166 from Chloroflexus aurantiacus.
Febs J., 2026

PubMed Abstract: β-1,2-Glucans are glucose polymers widely distributed in nature and play various physiological roles in the interactions between organisms such as pathogenicity and symbiosis. While various β-1,2-glucan-degrading enzymes have been identified recently, transporters incorporating β-1,2-glucans are still poorly characterized. In this study, we have found a β-1,2-glucan binding protein of ABC transporter from Chloroflexus aurantiacus Y-400-fl, a filamentous anoxygenic phototrophic bacterium. The protein showed a clear affinity for linear β-1,2-glucan in the gel shift assay. Isothermal titration calorimetric analysis revealed high binding affinities for both linear and cyclic β-1,2-glucans, unlike for the barley β-glucan. The recorded binding constants were high for the binding of the ABC transporter to β-1,2-glucans. The observed unfavorable negative entropy change may have resulted from conformational restraints upon complex formation. Complex structures with linear β-1,2-glucan and cyclic β-1,2-glucans with degrees of polymerization of 17-20 were obtained using X-ray crystallography. Ten glucose units, designated A-J from the nonreducing end, were shared among the substrates in the complexes. Unit G is recognized by W74, W308, and D336, which are highly conserved residues within the phylogenetic group Chy400_4166. The substrate-binding mode of Chy400_4166 is completely different from that of the β-1,2-glucooligosaccharide-binding protein from Listeria innocua. The discovery of a new type of β-1,2-glucan-related binding protein has expanded our understanding of the metabolism of β-1,2-glucans.

PubMed: 42108234
DOI: 10.1111/febs.70576

Experimental method

X-RAY DIFFRACTION (1.95 Å)