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Structure and mechanism of endo/exocellulase E4 from Thermomonospora fusca

Nature Structural Biology volume 4, pages 810–818 (1997)Cite this article

Abstract

Cellulase E4 from Thermomonospora fusca is unusual in that it has characteristics of both exo- and endo-cellulases. Here we report the crystal structure of a 68K Mr fragment of E4 (E4-68) at 1.9 Å resolution. E4-68 contains both a family 9 catalytic domain, exhibiting an (α/α)6 barrel fold, and a family III cellulose binding domain, having an antiparallel β-sandwich fold. While neither of these folds is novel, E4-68 provides the first cellulase structure having interacting catalytic and cellulose binding domains. The complexes of E4-68 with cellopentaose, cellotriose and cellobiose reveal conformational changes associated with ligand binding and allow us to propose a catalytic mechanism for family 9 enzymes. We also provide evidence that E4 has two novel characteristics: first it combines exo- and endo- activities and second, when it functions as an exo-cellulase, it cleaves off cellotetraose units.

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Author notes

  1. Joshua Sakon

    Present address: Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas, 72701, USA

Authors and Affiliations

  1. Section of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, New York, 14853, USA

    Joshua Sakon, Diana Irwin, David B. Wilson & P. Andrew Karplus

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Sakon, J., Irwin, D., Wilson, D. et al. Structure and mechanism of endo/exocellulase E4 from Thermomonospora fusca. Nat Struct Mol Biol 4, 810–818 (1997). https://doi.org/10.1038/nsb1097-810

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