PDBsum entry: 1h0b

Hydrolase

PDB id: 1h0b

Contents

Protein chains

227 a.a. *

Ligands

EPE ×2

Waters ×280

* Residue conservation analysis

PDB id:

1h0b

Name:

Hydrolase

Title:

Endoglucanase cel12a from rhodothermus marinus

Structure:

Cellulase. Chain: a, b. Fragment: catalytic domain, residues 38-260. Engineered: yes

Source:

Rhodothermus marinus. Organism_taxid: 29549. Expressed in: escherichia coli. Expression_system_taxid: 511693. Expression_system_variant: lambda(de3)-lysogen.

Resolution:

1.8Å R-factor: 0.173 R-free: 0.194

Authors:

S.J.Crennell,G.O.Hreggvidsson,E.Nordberg-Karlsson

Key ref:

S.J.Crennell et al. (2002). The structure of Rhodothermus marinus Cel12A, a highly thermostable family 12 endoglucanase, at 1.8 A resolution. J Mol Biol, 320, 883-897. PubMed id: 12095262 DOI: 10.1016/S0022-2836(02)00446-1

Date:

17-Jun-02 Release date: 12-Jun-03

Protein chains

O33897  (O33897_RHOMR) -  Cellulase

Seq: 260 a.a.

Struc: 227 a.a.*

* PDB and UniProt seqs differ at 18 residue positions (black crosses)

Enzyme reactions

• Enzyme class: E.C.3.2.1.4 - Cellulase.
• Reaction: Endohydrolysis of 1,4-beta-D-glucosidic linkages in cellulose, lichenin and cereal beta-D-glucans.

 Gene Ontology (GO) functional annotation 

• Biological process: polysaccharide catabolic process (1 term)
• Biochemical function: hydrolase activity, hydrolyzing O-glycosyl compounds (2 terms)

DOI no: 10.1016/S0022-2836(02)00446-1

J Mol Biol 320:883-897 (2002)

PubMed id: 12095262

The structure of Rhodothermus marinus Cel12A, a highly thermostable family 12 endoglucanase, at 1.8 A resolution.

S.J.Crennell, G.O.Hreggvidsson, E.Nordberg Karlsson.

ABSTRACT

Cellulose is one of the most abundant polysaccharides in nature and microorganisms have developed a comprehensive system for enzymatic breakdown of this ubiquitous carbon source, a subject of much interest in the biotechnology industry. Rhodothermus marinus produces a hyperthermostable cellulase, with a temperature optimum of more than 90 degrees C, the structure of which is presented here to 1.8 A resolution. The enzyme has been classified into glycoside hydrolase family 12; this is the first structure of a thermophilic member of this family to have been solved. The beta-jelly roll fold observed has identical topology to those of the two mesophilic members of the family whose structures have been elucidated previously. A Hepes buffer molecule bound in the active site may have triggered a conformational change to an active configuration as the two catalytic residues Glu124 and Glu207, together with dependent residues, are observed in a conformation similar to that seen in the structure of Streptomyces lividans CelB2 complexed with an inhibitor. The structural similarity between this cellulase and the mesophilic enzymes serves to highlight features that may be responsible for its thermostability, chiefly an increase in ion pair number and the considerable stabilisation of a mobile region seen in S. lividans CelB2. Additional aromatic residues in the active site region may also contribute to the difference in thermophilicity.

Selected figure(s)

Figure 1.
Figure 1. Schematic representation of the structure of R. marinus Cel12A, with sheet A shown in black and sheet B grey, drawn using MOLSCRIPT.[53] Individual strands are labelled according to their position within the sheets. The Hepes molecule bound in the active site is shown in a ball-and-stick representation.

Figure 4.
Figure 4. Schematic representations of the active sites of (a) Cel12A with Hepes bound and (b) CelB2 with 2-deoxy-2 fluorocellotrioside bound in the central -1 subsite, drawn using MOLSCRIPT[53] and Raster3D. [56] The amino acids that interact with cellulose are drawn with orange bonds, the inhibitor is shown in black (with the sugars in the -2 and -3 subsites of CelB2 drawn smaller for clarity), and hydrogen bonds as green dotted lines. The "cord" loop is coloured pale green.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2002, 320, 883-897) copyright 2002.

Figures were selected by the author.

Author's comment

See also 2bwa, 2bwc and 2bw8, for more recent structures of this protein with substrate bound.