Back to Search Start Over

The laterally acquired GH5 ZgEngAGH5_4 from the marine bacterium Zobellia galactanivorans is dedicated to hemicellulose hydrolysis

Authors :
Damien Thompson
Jérôme Dabin
Jonathan Dorival
Aurore Labourel
Sabine Genicot
Sophie Ruppert
Mirjam Czjzek
Adam Orłowski
Gurvan Michel
Maylis Chapelais-Baron
Melissa Gunnoo
Laboratoire de Biologie Intégrative des Modèles Marins (LBI2M)
Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Station biologique de Roscoff (SBR)
Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Bernal Institute [Limerick, Ireland]
University of Limerick (UL)
Source :
Biochemical Journal, Biochemical Journal, Portland Press, 2018, 475 (22), pp.3609-3628. ⟨10.1042/BCJ20180486⟩
Publication Year :
2018
Publisher :
Portland Press Ltd., 2018.

Abstract

Cell walls of marine macroalgae are composed of diverse polysaccharides that provide abundant carbon sources for marine heterotrophic bacteria. Among them, Zobellia galactanivorans is considered as a model for studying algae–bacteria interactions. The degradation of typical algal polysaccharides, such as agars or alginate, has been intensively studied in this model bacterium, but the catabolism of plant-like polysaccharides is essentially uncharacterized. Here, we identify a polysaccharide utilization locus in the genome of Z. galactanivorans, induced by laminarin (β-1,3-glucans), and containing a putative GH5 subfamily 4 (GH5_4) enzyme, currently annotated as a endoglucanase (ZgEngAGH5_4). A phylogenetic analysis indicates that ZgEngAGH5_4 was laterally acquired from an ancestral Actinobacteria. We performed the biochemical and structural characterization of ZgEngAGH5_4 and demonstrated that this GH5 is, in fact, an endo-β-glucanase, most active on mixed-linked glucan (MLG). Although ZgEngAGH5_4 and GH16 lichenases both hydrolyze MLG, these two types of enzymes release different series of oligosaccharides. Structural analyses of ZgEngAGH5_4 reveal that all the amino acid residues involved in the catalytic triad and in the negative glucose-binding subsites are conserved, when compared with the closest relative, the cellulase EngD from Clostridium cellulovorans, and some other GH5s. In contrast, the positive glucose-binding subsites of ZgEngAGH5_4 are different and this could explain the preference for MLG, with respect to cellulose or laminarin. Molecular dynamics computer simulations using different hexaoses reveal that the specificity for MLG occurs through the +1 and +2 subsites of the binding pocket that display the most important differences when compared with the structures of other GH5_4 enzymes.

Details

ISSN :
14708728 and 02646021
Volume :
475
Database :
OpenAIRE
Journal :
Biochemical Journal
Accession number :
edsair.doi.dedup.....b944543244bf4cd21bce0068585921ef
Full Text :
https://doi.org/10.1042/bcj20180486