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Complexity of the Ruminococcus flavefaciens cellulosome reflects an expansion in glycan recognition

2016; National Academy of Sciences; Volume: 113; Issue: 26 Linguagem: Inglês

10.1073/pnas.1601558113

1091-6490

I. Venditto, Ana S. Luís, Maja G. Rydahl, Julia Schückel, Vânia O. Fernandes, Silvia Vidal-Melgosa, Pedro Bule, Arun Goyal, Virgínia M. R. Pires, Catarina G. Dourado, L.M.A. Ferreira, Pedro M. Coutinho, Bernard Henrissat, John Knox, Arnaud Baslé, Shabir Najmudin, Harry J. Gilbert, William G. T. Willats, C.M.G.A. Fontes,

Enzyme Production and Characterization

Significance Plant cell wall (PCW) polysaccharide degradation is an important biological and industrial process. Noncatalytic carbohydrate binding modules (CBMs) fulfill a critical targeting function in PCW depolymerization. Ruminococcus flavefaciens synthesizes a highly efficient PCW degrading apparatus. Here, six previously unidentified R. flavefaciens CBM families were identified that targeted β-glucans, β-mannans, and pectins. Crystal structures of these CBMs revealed that recognition of β-glucans and β-mannans was mediated by differences in the conformation of conserved aromatic residues in the ligand binding cleft. A cluster of basic residues in CBM77 confers calcium-independent recognition of homogalacturonan. This report shows that the expansion of protein modules in the cellulosome of R. flavefaciens contributes to an extended CBM profile that supports efficient PCW degradation.