1iew
From Proteopedia
(New page: 200px<br /><applet load="1iew" size="450" color="white" frame="true" align="right" spinBox="true" caption="1iew, resolution 2.55Å" /> '''Crystal structure of...) |
|||
| Line 1: | Line 1: | ||
| - | [[Image:1iew.gif|left|200px]]<br /><applet load="1iew" size=" | + | [[Image:1iew.gif|left|200px]]<br /><applet load="1iew" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1iew, resolution 2.55Å" /> | caption="1iew, resolution 2.55Å" /> | ||
'''Crystal structure of barley beta-D-glucan glucohydrolase isoenzyme Exo1 in complex with 2-deoxy-2-fluoro-alpha-D-glucoside'''<br /> | '''Crystal structure of barley beta-D-glucan glucohydrolase isoenzyme Exo1 in complex with 2-deoxy-2-fluoro-alpha-D-glucoside'''<br /> | ||
==Overview== | ==Overview== | ||
| - | BACKGROUND: Barley beta-D-glucan glucohydrolases represent family 3 | + | BACKGROUND: Barley beta-D-glucan glucohydrolases represent family 3 glycoside hydrolases that catalyze the hydrolytic removal of nonreducing glucosyl residues from beta-D-glucans and beta-D-glucooligosaccharides. After hydrolysis is completed, glucose remains bound in the active site. RESULTS: When conduritol B epoxide and 2', 4'-dinitrophenyl 2-deoxy-2-fluoro-beta-D-glucopyranoside are diffused into enzyme crystals, they displace the bound glucose and form covalent glycosyl-enzyme complexes through the Odelta1 of D285, which is thereby identified as the catalytic nucleophile. A nonhydrolyzable S-glycosyl analog, 4(I), 4(III), 4(V)-S-trithiocellohexaose, also diffuses into the active site, and a S-cellobioside moiety positions itself at the -1 and +1 subsites. The glycosidic S atom of the S-cellobioside moiety forms a short contact (2.75 A) with the Oepsilon2 of E491, which is likely to be the catalytic acid/base. The glucopyranosyl residues of the S-cellobioside moiety are not distorted from the low-energy 4C(1) conformation, but the glucopyranosyl ring at the +1 subsite is rotated and translated about the linkage. CONCLUSIONS: X-ray crystallography is used to define the three key intermediates during catalysis by beta-D-glucan glucohydrolase. Before a new hydrolytic event begins, the bound product (glucose) from the previous catalytic reaction is displaced by the incoming substrate, and a new enzyme-substrate complex is formed. The second stage of the hydrolytic pathway involves glycosidic bond cleavage, which proceeds through a double-displacement reaction mechanism. The crystallographic analysis of the S-cellobioside-enzyme complex with quantum mechanical modeling suggests that the complex might mimic the oxonium intermediate rather than the enzyme-substrate complex. |
==About this Structure== | ==About this Structure== | ||
| - | 1IEW is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Hordeum_vulgare Hordeum vulgare] with NAG and G2F as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Glucan_1,3-beta-glucosidase Glucan 1,3-beta-glucosidase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.58 3.2.1.58] Full crystallographic information is available from [http:// | + | 1IEW is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Hordeum_vulgare Hordeum vulgare] with <scene name='pdbligand=NAG:'>NAG</scene> and <scene name='pdbligand=G2F:'>G2F</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Glucan_1,3-beta-glucosidase Glucan 1,3-beta-glucosidase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.58 3.2.1.58] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1IEW OCA]. |
==Reference== | ==Reference== | ||
| Line 15: | Line 15: | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: DeGori, R.]] | [[Category: DeGori, R.]] | ||
| - | [[Category: Fincher, G | + | [[Category: Fincher, G B.]] |
[[Category: Hrmova, M.]] | [[Category: Hrmova, M.]] | ||
| - | [[Category: Smith, B | + | [[Category: Smith, B J.]] |
| - | [[Category: Varghese, J | + | [[Category: Varghese, J N.]] |
[[Category: G2F]] | [[Category: G2F]] | ||
[[Category: NAG]] | [[Category: NAG]] | ||
[[Category: 2-domain fold]] | [[Category: 2-domain fold]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 13:11:10 2008'' |
Revision as of 11:11, 21 February 2008
|
Crystal structure of barley beta-D-glucan glucohydrolase isoenzyme Exo1 in complex with 2-deoxy-2-fluoro-alpha-D-glucoside
Overview
BACKGROUND: Barley beta-D-glucan glucohydrolases represent family 3 glycoside hydrolases that catalyze the hydrolytic removal of nonreducing glucosyl residues from beta-D-glucans and beta-D-glucooligosaccharides. After hydrolysis is completed, glucose remains bound in the active site. RESULTS: When conduritol B epoxide and 2', 4'-dinitrophenyl 2-deoxy-2-fluoro-beta-D-glucopyranoside are diffused into enzyme crystals, they displace the bound glucose and form covalent glycosyl-enzyme complexes through the Odelta1 of D285, which is thereby identified as the catalytic nucleophile. A nonhydrolyzable S-glycosyl analog, 4(I), 4(III), 4(V)-S-trithiocellohexaose, also diffuses into the active site, and a S-cellobioside moiety positions itself at the -1 and +1 subsites. The glycosidic S atom of the S-cellobioside moiety forms a short contact (2.75 A) with the Oepsilon2 of E491, which is likely to be the catalytic acid/base. The glucopyranosyl residues of the S-cellobioside moiety are not distorted from the low-energy 4C(1) conformation, but the glucopyranosyl ring at the +1 subsite is rotated and translated about the linkage. CONCLUSIONS: X-ray crystallography is used to define the three key intermediates during catalysis by beta-D-glucan glucohydrolase. Before a new hydrolytic event begins, the bound product (glucose) from the previous catalytic reaction is displaced by the incoming substrate, and a new enzyme-substrate complex is formed. The second stage of the hydrolytic pathway involves glycosidic bond cleavage, which proceeds through a double-displacement reaction mechanism. The crystallographic analysis of the S-cellobioside-enzyme complex with quantum mechanical modeling suggests that the complex might mimic the oxonium intermediate rather than the enzyme-substrate complex.
About this Structure
1IEW is a Single protein structure of sequence from Hordeum vulgare with and as ligands. Active as Glucan 1,3-beta-glucosidase, with EC number 3.2.1.58 Full crystallographic information is available from OCA.
Reference
Catalytic mechanisms and reaction intermediates along the hydrolytic pathway of a plant beta-D-glucan glucohydrolase., Hrmova M, Varghese JN, De Gori R, Smith BJ, Driguez H, Fincher GB, Structure. 2001 Nov;9(11):1005-16. PMID:11709165
Page seeded by OCA on Thu Feb 21 13:11:10 2008
