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s target in plant cell walls

Titles target in plant cell walls
Publication TypeJournal Article
Year of Publication2013
AuthorsWang, T, Park, YB, Caporini, MA, Rosay, M, Zhong, LH, Cosgrove, DJ, Hong, M
JournalProceedings of the National Academy of Sciences of the United States of America
Date Published10
Type of ArticleArticle
ISBN Number0027-8424
Accession NumberWOS:000325395600045
Keywordsarabidopsis, bacterial, binding, carbohydrate-binding module, CBM, cellulose, crystal-structure, dynamic nuclear-polarization, expansin, polysaccharides, Spectroscopy, spin-lattice-relaxation, xyloglucan

lear polarization (DNP) and differential isotopic labeling of expansin and polysaccharides, we have now determined the functional binding target of expansin in the Arabidopsis thaliana CW. By transferring the electron polarization of a biradical dopant to the nuclei, DNP allowed selective detection of C-13 spin diffusion from trace concentrations of C-13, N-15-labeled expansin in the CW to nearby polysaccharides. From the spin diffusion data of wild-type and mutant expansins, we conclude that to loosen the CW, expansin binds highly specific cellulose domains enriched in xyloglucan, whereas more abundant binding to pectins is unrelated to activity. Molecular dynamics simulations indicate short C-13-C-13 distances of 4-6 angstrom between a hydrophobic surface of the cellulose microfibril and an aromatic motif on the expansin surface, consistent with the observed NMR signals. DNP-enhanced 2D C-13 correlation spectra further reveal that the expansin-bound cellulose has altered conformation and is enriched in xyloglucan, thus providing unique insight into the mechanism of CW loosening. DNP-enhanced NMR provides a powerful, generalizable approach for investigating protein binding to complex macromolecular targets.

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