Liberato, Marcelo V.; Silveira, Rodrigo L.; Prates, Erica T.; de Araujo, Evandro A.; Pellegrini, Vanessa O. A.; Camilo, Cesar M.; Kadowaki, Marco A.; Neto, Mario de O.; Popov, Alexander; Skaf, Munir S.; Polikarpov, Igor
Molecular characterization of a family 5 glycoside hydrolase suggests an induced-fit enzymatic mechanism
SCIENTIFIC REPORTS, 6 Art. No. 23473, APR 1 2016

Glycoside hydrolases (GHs) play fundamental roles in the decomposition of lignocellulosic biomaterials. Here, we report the full-length structure of a cellulase from Bacillus licheniformis (BlCel5B), a member of the GH5 subfamily 4 that is entirely dependent on its two ancillary modules (Ig-like module and CBM46) for catalytic activity. Using X-ray crystallography, small-angle X-ray scattering and molecular dynamics simulations, we propose that the C-terminal CBM46 caps the distal N-terminal catalytic domain (CD) to establish a fully functional active site via a combination of large-scale multidomain conformational selection and induced-fit mechanisms. The Ig-like module is pivoting the packing and unpacking motions of CBM46 relative to CD in the assembly of the binding subsite. This is the first example of a multidomain GH relying on large amplitude motions of the CBM46 for assembly of the catalytically competent form of the enzyme.


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