The active site of a carbohydrate esterase displays divergent catalytic and noncatalytic binding functions

Autor: Evangelos Topakas, Benedita A. Pinheiro, James E. Flint, V.A. Money, Cedric Montanier, José A. M. Prates, Arun Goyal, Carlos M. G. A. Fontes, Gideon J. Davies, Alan Cartmell, David N. Bolam, Virgínia M. R. Pires, Eleanor J. Dodson, Katarina Kolenova, Harry J. Gilbert, Carl Morland, Atsushi Izumi, Henrik Stålbrand
Přispěvatelé: Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle (UoN), York Structural Biology Laboratory, Department of Chemistry, University of York [York, UK], Universidade Técnica de Lisboa, Lund University [Lund], Biotechnology and Biological Sciences Research Council, Fundacao para a Ciencia e Technologia, Royal Society Wolfson Research Merit Award, Davies, Gideon J, Gilbert, Harry J
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Zdroj: CIÊNCIAVITAE
PLOS BIOLOGY
PLoS Biology, Vol 7, Iss 3, p e71 (2009)
Scopus-Elsevier
PLoS Biology
PLoS Biology, Public Library of Science, 2009, 7 (3), pp.687-697. ⟨10.1371/journal.pbio.1000071⟩
PLoS biology, 2009, Vol.7(3), pp.e1000071 [Peer Reviewed Journal]
Plos Biology 3 (7), 687-697. (2009)
ISSN: 1544-9173
1545-7885
DOI: 10.1371/journal.pbio.1000071⟩
Popis: Multifunctional proteins, which play a critical role in many biological processes, have typically evolved through the recruitment of different domains that have the required functional diversity. Thus the different activities displayed by these proteins are mediated by spatially distinct domains, consistent with the specific chemical requirements of each activity. Indeed, current evolutionary theory argues that the colocalization of diverse activities within an enzyme is likely to be a rare event, because it would compromise the existing activity of the protein. In contrast to this view, a potential example of multifunctional recruitment into a single protein domain is provided by CtCel5C-CE2, which contains an N-terminal module that displays cellulase activity and a C-terminal module, CtCE2, which exhibits a noncatalytic cellulose-binding function but also shares sequence identity with the CE2 family of esterases. Here we show that, unlike other CE2 members, the CtCE2 domain displays divergent catalytic esterase and noncatalytic carbohydrate binding functions. Intriguingly, these diverse activities are housed within the same site on the protein. Thus, a critical component of the active site of CtCE2, the catalytic Ser-His dyad, in harness with inserted aromatic residues, confers noncatalytic binding to cellulose whilst the active site of the domain retains its esterase activity. CtCE2 catalyses deacetylation of noncellulosic plant structural polysaccharides to deprotect these substrates for attack by other enzymes. Yet it also acts as a cellulose-binding domain, which promotes the activity of the appended cellulase on recalcitrant substrates. The CE2 family encapsulates the requirement for multiple activities by biocatalysts that attack challenging macromolecular substrates, including the grafting of a second, powerful and discrete noncatalytic binding functionality into the active site of an enzyme. This article provides a rare example of "gene sharing,'' where the introduction of a second functionality into the active site of an enzyme does not compromise the original activity of the biocatalyst. Copyright: © 2009 Montanier et al. This is an open-access article distributed under.
Databáze: OpenAIRE
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