PDBsum entry: 1aoh

Cellulosome subunit

PDB id: 1aoh

Contents

Protein chains

143 a.a. *

Waters ×381

* Residue conservation analysis

PDB id:

1aoh

Name:

Cellulosome subunit

Title:

Single cohesin domain from the scaffolding protein cipa of the clostridium thermocellum cellulosome

Structure:

Cellulosome-integrating protein cipa. Chain: a, b. Fragment: cohesin domain. Engineered: yes

Source:

Clostridium thermocellum. Organism_taxid: 1515. Cell_line: bl21. Cellular_location: cytoplasm. Gene: laci. Expressed in: escherichia coli. Expression_system_taxid: 562. Expression_system_cell_line: bl21.

Biol. unit:

Monomer (from PDB file)

Resolution:

1.70Å R-factor: 0.194

Authors:

P.M.Alzari,G.Tavares

Key ref:

G.A.Tavares et al. (1997). The crystal structure of a type I cohesin domain at 1.7 A resolution. J Mol Biol, 273, 701-713. PubMed id: 9402065 DOI: 10.1006/jmbi.1997.1326

Date:

03-Jul-97 Release date: 08-Jul-98

Protein chains

Q06851  (CIPA_CLOTH) -  Cellulosomal-scaffolding protein A

Seq: 1853 a.a.

Struc: 143 a.a.

 Gene Ontology (GO) functional annotation 

• Cellular component: peptidoglycan-based cell wall (1 term)
• Biological process: polysaccharide catabolic process (1 term)
• Biochemical function: carbohydrate binding (1 term)

DOI no: 10.1006/jmbi.1997.1326

J Mol Biol 273:701-713 (1997)

PubMed id: 9402065

The crystal structure of a type I cohesin domain at 1.7 A resolution.

G.A.Tavares, P.Béguin, P.M.Alzari.

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.

Selected figure(s)

Figure 6.
Figure 6. Cohesin “dimer” interactions. The surface contact area on the four-stranded (8-3-6-5) β-sheet of one of the domains is shown in red. The Figure was produced with the program GRASP [Nicholls et al 1993].

Figure 7.
Figure 7. Stereoview showing the hydrogen-bonding interactions (in red) that stabilize the conformation of the exposed loops 4–5 and 6–7.

The above figures are reprinted by permission from Elsevier: J Mol Biol (1997, 273, 701-713) copyright 1997.

Figures were selected by an automated process.