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Structural characterization of a unique marine animal family 7 cellobiohydrolase suggests a mechanism of cellulase salt tolerance

DOI: 10.1073/pnas.1301502110 DOI Help
PMID: 23733951 PMID Help

Authors: Marcelo Kern (University of York) , John E. Mcgeehan (University of Portsmouth) , Simon D. Streeter (University of Portsmouth) , Richard N. A. Martin (University of Portsmouth) , Katrin Besser (University of York) , Luisa Elias (University of York) , Will Eborall (University of York) , Graham P. Malyon (University of Portsmouth) , Christina M. Payne (University of Kentucky) , Michael E. Himmel (National Renewable Energy Laboratory) , Kirk Schnorr (Novozymes A/S) , Gregg T. Beckham (National Renewable Energy Laboratory) , Simon M. Cragg (University of Portsmouth) , Neil C. Bruce (University of York) , Simon J. Mcqueen-mason (University of York)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: Proceedings Of The National Academy Of Sciences , VOL 110 (25) , PAGES 10189 - 10194

State: Published (Approved)
Published: June 2013
Diamond Proposal Number(s): 7131

Abstract: Nature uses a diversity of glycoside hydrolase (GH) enzymes to convert polysaccharides to sugars. As lignocellulosic biomass deconstruction for biofuel production remains costly, natural GH diversity offers a starting point for developing industrial enzymes, and fungal GH family 7 (GH7) cellobiohydrolases, in particular, provide significant hydrolytic potential in industrial mixtures. Recently, GH7 enzymes have been found in other kingdoms of life besides fungi, including in animals and protists. Here, we describe the in vivo spatial expression distribution, properties, and structure of a unique endogenous GH7 cellulase from an animal, the marine wood borer Limnoria quadripunctata (LqCel7B). RT-quantitative PCR and Western blot studies show that LqCel7B is expressed in the hepatopancreas and secreted into the gut for wood degradation. We produced recombinant LqCel7B, with which we demonstrate that LqCel7B is a cellobiohydrolase and obtained four high-resolution crystal structures. Based on a crystallographic and computational comparison of LqCel7B to the well-characterized Hypocrea jecorina GH7 cellobiohydrolase, LqCel7B exhibits an extended substrate-binding motif at the tunnel entrance, which may aid in substrate acquisition and processivity. Interestingly, LqCel7B exhibits striking surface charges relative to fungal GH7 enzymes, which likely results from evolution in marine environments. We demonstrate that LqCel7B stability and activity remain unchanged, or increase at high salt concentration, and that the L. quadripunctata GH mixture generally contains cellulolytic enzymes with highly acidic surface charge compared with enzymes derived from terrestrial microbes. Overall, this study suggests that marine cellulases offer significant potential for utilization in high-solids industrial biomass conversion processes.

Journal Keywords: Biofuels; Biomass; Cellulase; Cellulose; Crustacea; Crystallography; X-Ray; Digestive; Enzyme; Hypocrea; Protein; Tertiary; Salt-Tolerance; Seawater; Structure-Activity; Substrate Specificity

Subject Areas: Biology and Bio-materials, Energy

Instruments: I02-Macromolecular Crystallography , I04-1-Macromolecular Crystallography (fixed wavelength) , I04-Macromolecular Crystallography

Other Facilities: No

Added On: 20/06/2013 11:50

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