5T7A

Crystal structure of Br derivative BhCBM56

Summary for 5T7A

• Entry DOI: 10.2210/pdb5t7a/pdb
• Descriptor: BH0236 protein, 1,2-ETHANEDIOL, BROMIDE ION, ... (4 entities in total)
• Functional Keywords: carbohydrate binding module, sugar binding protein
• Biological source: Bacillus halodurans (strain ATCC BAA-125 / DSM 18197 / FERM 7344 / JCM 9153 / C-125)
• Total number of polymer chains: 2
• Total formula weight: 27848.98

Authors

Pluvinage, B.,Boraston, A.B. (deposition date: 2016-09-02, release date: 2017-08-23, Last modification date: 2024-03-06)

Primary citation

Hettle, A.,Fillo, A.,Abe, K.,Massel, P.,Pluvinage, B.,Langelaan, D.N.,Smith, S.P.,Boraston, A.B.
Properties of a family 56 carbohydrate-binding module and its role in the recognition and hydrolysis of beta-1,3-glucan.
J. Biol. Chem., 292:16955-16968, 2017

PubMed Abstract: BH0236 from is a multimodular β-1,3-glucanase comprising an N-terminal family 81 glycoside hydrolase catalytic module, an internal family 6 carbohydrate-binding module (CBM) that binds the nonreducing end of β-1,3-glucan chains, and an uncharacterized C-terminal module classified into CBM family 56. Here, we determined that this latter CBM, BhCBM56, bound the soluble β-1,3-glucan laminarin with a dissociation constant ( ) of ∼26 μm and displayed higher affinity for insoluble β-1,3-glucans with values of ∼2-10 μm but lacked affinity for β-1,3-glucooligosaccharides. The X-ray crystal structure of BhCBM56 and NMR-derived chemical shift mapping of the binding site revealed a β-sandwich fold, with the face of one β-sheet possessing the β-1,3-glucan-binding surface. On the basis of the functional and structural properties of BhCBM56, we propose that it binds a quaternary polysaccharide structure, most likely the triple helix adopted by polymerized β-1,3-glucans. Consistent with the BhCBM56 and BhCBM6/56 binding profiles, deletion of the CBM56 from BH0236 decreased activity of the enzyme on the insoluble β-1,3-glucan curdlan but not on soluble laminarin; additional deletion of the CBM6 also did not affect laminarin degradation but further decreased curdlan hydrolysis. The pseudo-atomic solution structure of BH0236 determined by small-angle X-ray scattering revealed structural insights into the nature of avid binding by the BhCBM6/56 pair and how the orientation of the active site in the catalytic module factors into recognition and degradation of β-1,3-glucans. Our findings reinforce the notion that catalytic modules and their cognate CBMs have complementary specificities, including targeting of polysaccharide quaternary structure.

PubMed: 28827308
DOI: 10.1074/jbc.M117.806711

Experimental method

X-RAY DIFFRACTION (1.6 Å)