1AOH

SINGLE COHESIN DOMAIN FROM THE SCAFFOLDING PROTEIN CIPA OF THE CLOSTRIDIUM THERMOCELLUM CELLULOSOME

Summary for 1AOH

• Entry DOI: 10.2210/pdb1aoh/pdb
• Descriptor: Cellulosomal-scaffolding protein A (2 entities in total)
• Functional Keywords: cellulosome subunit, b-barrel, cellulose degradation, structural protein
• Biological source: Clostridium thermocellum (strain ATCC 27405 / DSM 1237 / NBRC 103400 / NCIMB 10682 / NRRL B-4536 / VPI 7372) (Ruminiclostridium thermocellum)
• Total number of polymer chains: 2
• Total formula weight: 31521.48

Authors

Alzari, P.M.,Tavares, G. (deposition date: 1997-07-03, release date: 1998-07-08, Last modification date: 2024-02-07)

Primary citation

Tavares, G.A.,Beguin, P.,Alzari, P.M.
The crystal structure of a type I cohesin domain at 1.7 A resolution.
J.Mol.Biol., 273:701-713, 1997

PubMed Abstract: 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.

PubMed: 9402065
DOI: 10.1006/jmbi.1997.1326

Experimental method

X-RAY DIFFRACTION (1.7 Å)