1aoh
From Proteopedia
SINGLE COHESIN DOMAIN FROM THE SCAFFOLDING PROTEIN CIPA OF THE CLOSTRIDIUM THERMOCELLUM CELLULOSOME
Overview
The 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.
About this Structure
1AOH is a Single protein structure of sequence from Clostridium thermocellum. Full crystallographic information is available from OCA.
Reference
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 Page seeded by OCA on Fri May 2 10:30:58 2008
