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The solution structure of the CBM4-2 carbohydrate binding module from a thermostable Rhodothermus marinus xylanase

Lookup NU author(s): Emeritus Professor Harry Gilbert


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The solution structure is presented for the second family 4 carbohydrate binding module (CBM4-2) of xylanase 10A from the thermophilic bacterium Rhodothermus marinus. CBM4-2, which binds xylan tightly, has a beta-sandwich structure formed by I I strands, and contains a prominent cleft. From NMR titrations, it is shown that the cleft is the binding site for xylan, and that the main amino acids interacting with xylan are Asn31, Tyr69, Glu72, Phe110, Arg115, and His146. Key liganding residues are Tyr69 and Phe110, which form stacking interactions with the sugar. It is suggested that file loops Oil which the rings are displayed can alter their conformation on substrate binding, which may have functional importance. Comparison both with other family 4 cellulose binding modules and with the structurally similar family 22 xylan binding module shows that the key aromatic residues are in similar positions, and that the bottom of the cleft is much more hydrophobic in the cellulose binding module,, than the xylan binding proteins. It is concluded that substrate specificity is determined by a combination of ring Orientation and the nature of the residues lining the bottom of the binding cleft.

Publication metadata

Author(s): Simpson PJ, Jamieson SJ, Abou-Hachem M, Karlsson EN, Gilbert HJ, Holst O, Williamson MP

Publication type: Article

Publication status: Published

Journal: Biochemistry

Year: 2002

Volume: 41

Issue: 18

Pages: 5712-5719

ISSN (print): 0006-2960

ISSN (electronic): 1520-4995

Publisher: American Chemical Society


DOI: 10.1021/bi012093i


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