2exo
From Proteopedia
(New page: 200px<br /><applet load="2exo" size="450" color="white" frame="true" align="right" spinBox="true" caption="2exo, resolution 1.8Å" /> '''CRYSTAL STRUCTURE OF ...) |
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| - | [[Image:2exo.jpg|left|200px]]<br /><applet load="2exo" size=" | + | [[Image:2exo.jpg|left|200px]]<br /><applet load="2exo" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="2exo, resolution 1.8Å" /> | caption="2exo, resolution 1.8Å" /> | ||
'''CRYSTAL STRUCTURE OF THE CATALYTIC DOMAIN OF THE BETA-1,4-GLYCANASE CEX FROM CELLULOMONAS FIMI'''<br /> | '''CRYSTAL STRUCTURE OF THE CATALYTIC DOMAIN OF THE BETA-1,4-GLYCANASE CEX FROM CELLULOMONAS FIMI'''<br /> | ||
==Overview== | ==Overview== | ||
| - | beta-1,4-Glycanases, principally cellulases and xylanases, are responsible | + | beta-1,4-Glycanases, principally cellulases and xylanases, are responsible for the hydrolysis of plant biomass. The bifunctional beta-1,4-xylanase/glucanase Cex from the bacterium Cellulomonas fimi, one of a large family of cellulases/xylanases, depolymerizes oligosaccharides and releases a disaccharide unit from the substrate nonreducing end. Hydrolysis occurs with net retention of the anomeric configuration of the sugar through a double-displacement mechanism involving a covalent glycosyl-enzyme intermediate. The active site nucleophile, Glu233, has been unambiguously identified by trapping of such an intermediate [Tull et al. (1991) J. Biol. Chem. 266, 15621-15625] and the acid/base catalyst, Glu127, by detailed kinetic analysis of mutants [MacLeod et al. (1994) Biochemistry 33, 6371-6376]. However, little is known about the enzyme's overall folding and its active site architecture. We report here the high-resolution crystal structure of the catalytic domain of Cex. The atomic structure refinement results in a model that includes 2400 protein atoms and 45 water molecules, with an R-factor of 0.217 for data extending to 1.8-A resolution. The protein forms an eight-parallel-stranded alpha/beta-barrel, which is a novel folding pattern for a microbial beta-glycanase. The active site, inferred from the location of Glu233, Glu127, and other conserved residues, is an open cleft on the carboxy-terminal end of the alpha/beta-barrel. An extensive hydrogen-bonding network stabilizes the ionization states of the key residues; in particular, the Asp235-His205-Glu233 hydrogen-bonding network may play a role in modulating the ionization state of Glu233 and in controlling local charge balance during the reaction. |
==About this Structure== | ==About this Structure== | ||
| - | 2EXO is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Cellulomonas_fimi Cellulomonas fimi]. Active as [http://en.wikipedia.org/wiki/Cellulose_1,4-beta-cellobiosidase Cellulose 1,4-beta-cellobiosidase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.91 3.2.1.91] Full crystallographic information is available from [http:// | + | 2EXO is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Cellulomonas_fimi Cellulomonas fimi]. Active as [http://en.wikipedia.org/wiki/Cellulose_1,4-beta-cellobiosidase Cellulose 1,4-beta-cellobiosidase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.91 3.2.1.91] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2EXO OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Cellulose 1,4-beta-cellobiosidase]] | [[Category: Cellulose 1,4-beta-cellobiosidase]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Gilkes, N | + | [[Category: Gilkes, N R.]] |
| - | [[Category: Rose, D | + | [[Category: Rose, D R.]] |
[[Category: White, A.]] | [[Category: White, A.]] | ||
| - | [[Category: Withers, S | + | [[Category: Withers, S G.]] |
[[Category: hydrolase (o-glycosyl)]] | [[Category: hydrolase (o-glycosyl)]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 17:15:37 2008'' |
Revision as of 15:15, 21 February 2008
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CRYSTAL STRUCTURE OF THE CATALYTIC DOMAIN OF THE BETA-1,4-GLYCANASE CEX FROM CELLULOMONAS FIMI
Overview
beta-1,4-Glycanases, principally cellulases and xylanases, are responsible for the hydrolysis of plant biomass. The bifunctional beta-1,4-xylanase/glucanase Cex from the bacterium Cellulomonas fimi, one of a large family of cellulases/xylanases, depolymerizes oligosaccharides and releases a disaccharide unit from the substrate nonreducing end. Hydrolysis occurs with net retention of the anomeric configuration of the sugar through a double-displacement mechanism involving a covalent glycosyl-enzyme intermediate. The active site nucleophile, Glu233, has been unambiguously identified by trapping of such an intermediate [Tull et al. (1991) J. Biol. Chem. 266, 15621-15625] and the acid/base catalyst, Glu127, by detailed kinetic analysis of mutants [MacLeod et al. (1994) Biochemistry 33, 6371-6376]. However, little is known about the enzyme's overall folding and its active site architecture. We report here the high-resolution crystal structure of the catalytic domain of Cex. The atomic structure refinement results in a model that includes 2400 protein atoms and 45 water molecules, with an R-factor of 0.217 for data extending to 1.8-A resolution. The protein forms an eight-parallel-stranded alpha/beta-barrel, which is a novel folding pattern for a microbial beta-glycanase. The active site, inferred from the location of Glu233, Glu127, and other conserved residues, is an open cleft on the carboxy-terminal end of the alpha/beta-barrel. An extensive hydrogen-bonding network stabilizes the ionization states of the key residues; in particular, the Asp235-His205-Glu233 hydrogen-bonding network may play a role in modulating the ionization state of Glu233 and in controlling local charge balance during the reaction.
About this Structure
2EXO is a Single protein structure of sequence from Cellulomonas fimi. Active as Cellulose 1,4-beta-cellobiosidase, with EC number 3.2.1.91 Full crystallographic information is available from OCA.
Reference
Crystal structure of the catalytic domain of the beta-1,4-glycanase cex from Cellulomonas fimi., White A, Withers SG, Gilkes NR, Rose DR, Biochemistry. 1994 Oct 25;33(42):12546-52. PMID:7918478
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