This old version of Proteopedia is provided for student assignments while the new version is undergoing repairs. Content and edits done in this old version of Proteopedia after March 1, 2026 will eventually be lost when it is retired in about June of 2026.
Apply for new accounts at the new Proteopedia. Your logins will work in both the old and new versions.
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
