1ee2
From Proteopedia
(New page: 200px<br /><applet load="1ee2" size="450" color="white" frame="true" align="right" spinBox="true" caption="1ee2, resolution 1.54Å" /> '''THE STRUCTURE OF STE...) |
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| - | [[Image:1ee2.jpg|left|200px]]<br /><applet load="1ee2" size=" | + | [[Image:1ee2.jpg|left|200px]]<br /><applet load="1ee2" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1ee2, resolution 1.54Å" /> | caption="1ee2, resolution 1.54Å" /> | ||
'''THE STRUCTURE OF STEROID-ACTIVE ALCOHOL DEHYDROGENASE AT 1.54 A RESOLUTION'''<br /> | '''THE STRUCTURE OF STEROID-ACTIVE ALCOHOL DEHYDROGENASE AT 1.54 A RESOLUTION'''<br /> | ||
==Overview== | ==Overview== | ||
| - | A structure determination in combination with a kinetic study of the | + | A structure determination in combination with a kinetic study of the steroid converting isozyme of horse liver alcohol dehydrogenase, SS-ADH, is presented. Kinetic parameters for the substrates, 5beta-androstane-3beta,17beta-ol, 5beta-androstane-17beta-ol-3-one, ethanol, and various secondary alcohols and the corresponding ketones are compared for the SS- and EE-isozymes which differ by nine amino acid substitutions and one deletion. Differences in substrate specificity and stereoselectivity are explained on the basis of individual kinetic rate constants for the underlying ordered bi-bi mechanism. SS-ADH was crystallized in complex with 3alpha,7alpha,12alpha-trihydroxy-5beta-cholan -24-acid (cholic acid) and NAD(+), but microspectrophotometric analysis of single crystals proved it to be a mixed complex containing 60-70% NAD(+) and 30-40% NADH. The crystals belong to the space group P2(1) with cell dimensions a = 55.0 A, b = 73.2 A, c = 92.5 A, and beta = 102.5 degrees. A 98% complete data set to 1.54-A resolution was collected at 100 K using synchrotron radiation. The structure was solved by the molecular replacement method utilizing EE-ADH as the search model. The major structural difference between the isozymes is a widening of the substrate channel. The largest shifts in C(alpha) carbon positions (about 5 A) are observed in the loop region, in which a deletion of Asp115 is found in the SS isozyme. SS-ADH easily accommodates cholic acid, whereas steroid substrates of similar bulkiness would not fit into the EE-ADH substrate site. In the ternary complex with NAD(+)/NADH, we find that the carboxyl group of cholic acid ligates to the active site zinc ion, which probably contributes to the strong binding in the ternary NAD(+) complex. |
==About this Structure== | ==About this Structure== | ||
| - | 1EE2 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Equus_caballus Equus caballus] with ZN, NAD and CHD as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Alcohol_dehydrogenase Alcohol dehydrogenase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.1.1.1 1.1.1.1] Full crystallographic information is available from [http:// | + | 1EE2 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Equus_caballus Equus caballus] with <scene name='pdbligand=ZN:'>ZN</scene>, <scene name='pdbligand=NAD:'>NAD</scene> and <scene name='pdbligand=CHD:'>CHD</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Alcohol_dehydrogenase Alcohol dehydrogenase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.1.1.1 1.1.1.1] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1EE2 OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Equus caballus]] | [[Category: Equus caballus]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Adolph, H | + | [[Category: Adolph, H W.]] |
[[Category: CHD]] | [[Category: CHD]] | ||
[[Category: NAD]] | [[Category: NAD]] | ||
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[[Category: steroid binding]] | [[Category: steroid binding]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:26:49 2008'' |
Revision as of 10:26, 21 February 2008
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THE STRUCTURE OF STEROID-ACTIVE ALCOHOL DEHYDROGENASE AT 1.54 A RESOLUTION
Overview
A structure determination in combination with a kinetic study of the steroid converting isozyme of horse liver alcohol dehydrogenase, SS-ADH, is presented. Kinetic parameters for the substrates, 5beta-androstane-3beta,17beta-ol, 5beta-androstane-17beta-ol-3-one, ethanol, and various secondary alcohols and the corresponding ketones are compared for the SS- and EE-isozymes which differ by nine amino acid substitutions and one deletion. Differences in substrate specificity and stereoselectivity are explained on the basis of individual kinetic rate constants for the underlying ordered bi-bi mechanism. SS-ADH was crystallized in complex with 3alpha,7alpha,12alpha-trihydroxy-5beta-cholan -24-acid (cholic acid) and NAD(+), but microspectrophotometric analysis of single crystals proved it to be a mixed complex containing 60-70% NAD(+) and 30-40% NADH. The crystals belong to the space group P2(1) with cell dimensions a = 55.0 A, b = 73.2 A, c = 92.5 A, and beta = 102.5 degrees. A 98% complete data set to 1.54-A resolution was collected at 100 K using synchrotron radiation. The structure was solved by the molecular replacement method utilizing EE-ADH as the search model. The major structural difference between the isozymes is a widening of the substrate channel. The largest shifts in C(alpha) carbon positions (about 5 A) are observed in the loop region, in which a deletion of Asp115 is found in the SS isozyme. SS-ADH easily accommodates cholic acid, whereas steroid substrates of similar bulkiness would not fit into the EE-ADH substrate site. In the ternary complex with NAD(+)/NADH, we find that the carboxyl group of cholic acid ligates to the active site zinc ion, which probably contributes to the strong binding in the ternary NAD(+) complex.
About this Structure
1EE2 is a Single protein structure of sequence from Equus caballus with , and as ligands. Active as Alcohol dehydrogenase, with EC number 1.1.1.1 Full crystallographic information is available from OCA.
Reference
Structural basis for substrate specificity differences of horse liver alcohol dehydrogenase isozymes., Adolph HW, Zwart P, Meijers R, Hubatsch I, Kiefer M, Lamzin V, Cedergren-Zeppezauer E, Biochemistry. 2000 Oct 24;39(42):12885-97. PMID:11041853
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