3d6e
Crystal structure of the engineered 1,3-1,4-beta-glucanase protein from Bacillus licheniformis
Structural highlights
FunctionEvolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedFamily 16 carbohydrate active enzyme members Bacillus licheniformis 1,3-1,4-beta-glucanase and Populus tremula x tremuloides xyloglucan endotransglycosylase (XET16-34) are highly structurally related but display different substrate specificities. Although the first binds linear gluco-oligosaccharides, the second binds branched xylogluco-oligosaccharides. Prior engineered nucleophile mutants of both enzymes are glycosynthases that catalyze the condensation between a glycosyl fluoride donor and a glycoside acceptor. With the aim of expanding the glycosynthase technology to produce designer oligosaccharides consisting of hybrids between branched xylogluco- and linear gluco-oligosaccharides, enzyme engineering on the negative subsites of 1,3-1,4-beta-glucanase to accept branched substrates has been undertaken. Removal of the 1,3-1,4-beta-glucanase major loop and replacement with that of XET16-34 to open the binding cleft resulted in a folded protein, which still maintained some beta-glucan hydrolase activity, but the corresponding nucleophile mutant did not display glycosynthase activity with either linear or branched glycosyl donors. Next, point mutations of the 1,3-1,4-beta-glucanase beta-sheets forming the binding site cleft were mutated to resemble XET16-34 residues. The final chimeric protein acquired binding affinity for xyloglucan and did not bind beta-glucan. Therefore, binding specificity has been re-engineered, but affinity was low and the nucleophile mutant of the chimeric enzyme did not show glycosynthase activity to produce the target hybrid oligosaccharides. Structural analysis by X-ray crystallography explains these results in terms of changes in the protein structure and highlights further engineering approaches toward introducing the desired activity. Proteins 2010. (c) 2010 Wiley-Liss, Inc. Re-engineering specificity in 1,3-1, 4-beta-glucanase to accept branched xyloglucan substrates.,Addington T, Calisto B, Alfonso-Prieto M, Rovira C, Fita I, Planas A Proteins. 2010 Sep 22. PMID:21069723[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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