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SINGLE COHESIN DOMAIN FROM THE SCAFFOLDING PROTEIN CIPA OF THE CLOSTRIDIUM THERMOCELLUM CELLULOSOMESINGLE COHESIN DOMAIN FROM THE SCAFFOLDING PROTEIN CIPA OF THE CLOSTRIDIUM THERMOCELLUM CELLULOSOME
Structural highlights
Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe quaternary organization of the cellulosome, a multi-enzymatic extracellular complex produced by cellulolytic bacteria, depends on specific interactions between dockerin domains, double EF-hand subunits carried by the catalytic components, and cohesin domains, individual receptor subunits linearly arranged within a non-catalytic scaffolding polypeptide. Cohesin-dockerin complexes with distinct specificities are also thought to mediate the attachment of cellulosomes to the cell membrane. We report here the crystal structure of a single cohesin domain from the scaffolding protein of Clostridium thermocellum. The cohesin domain folds into a nine-stranded beta-sandwich with an overall "jelly roll" topology, similar to that observed in bacterial cellulose-binding domains. Surface-exposed patches of conserved residues promote extensive intermolecular contacts in the crystal, and suggest a possible binding target for the EF-hand pair of the cognate dockerin domain. Comparative studies of cohesin domains indicate that, in spite of low sequence similarities and different functional roles, all cohesin domains share a common nine-stranded beta-barrel fold stabilized by a conserved hydrophobic core. The formation of stable cohesin-dockerin complexes requires the presence of Ca2+. However, the structure of the cohesin domain reported here reveals no obvious Ca2+-binding site, and previous experiments have failed to detect high affinity binding of Ca2+ to the unliganded dockerin domain of endoglucanase CelD. Based on structural and biochemical evidence, we propose a model of the cohesin-dockerin complex in which the dockerin domain requires complexation with its cohesin partner for protein stability and high-affinity Ca2+ binding. The crystal structure of a type I cohesin domain at 1.7 A resolution.,Tavares GA, Beguin P, Alzari PM J Mol Biol. 1997 Oct 31;273(3):701-13. PMID:9402065[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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