2a81
From Proteopedia
(New page: 200px<br /><applet load="2a81" size="350" color="white" frame="true" align="right" spinBox="true" caption="2a81, resolution 3.150Å" /> '''carboxymethylprolin...) |
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==Overview== | ==Overview== | ||
| - | The first step in the biosynthesis of the medicinally important carbapenem | + | The first step in the biosynthesis of the medicinally important carbapenem family of beta-lactam antibiotics is catalyzed by carboxymethylproline synthase (CarB), a unique member of the crotonase superfamily. CarB catalyzes formation of (2S,5S)-carboxymethylproline [(2S,5S)-t-CMP] from malonyl-CoA and l-glutamate semialdehyde. In addition to using a cosubstrate, CarB catalyzes C-C and C-N bond formation processes as well as an acyl-coenzyme A hydrolysis reaction. We describe the crystal structure of CarB in the presence and absence of acetyl-CoA at 2.24 A and 3.15 A resolution, respectively. The structures reveal that CarB contains a conserved oxy-anion hole probably required for decarboxylation of malonyl-CoA and stabilization of the resultant enolate. Comparison of the structures reveals that conformational changes (involving His(229)) in the cavity predicted to bind l-glutamate semialdehyde occur on (co)substrate binding. Mechanisms for the formation of the carboxymethylproline ring are discussed in the light of the structures and the accompanying studies using isotopically labeled substrates; cyclization via 1,4-addition is consistent with the observed labeling results (providing that hydrogen exchange at the C-6 position of carboxymethylproline does not occur). The side chain of Glu(131) appears to be positioned to be involved in hydrolysis of the carboxymethylproline-CoA ester intermediate. Labeling experiments ruled out the possibility that hydrolysis proceeds via an anhydride in which water attacks a carbonyl derived from Glu(131), as proposed for 3-hydroxyisobutyryl-CoA hydrolase. The structural work will aid in mutagenesis studies directed at altering the selectivity of CarB to provide intermediates for the production of clinically useful carbapenems. |
==About this Structure== | ==About this Structure== | ||
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[[Category: Pectobacterium carotovorum]] | [[Category: Pectobacterium carotovorum]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Batchelar, E | + | [[Category: Batchelar, E T.]] |
| - | [[Category: McDonough, M | + | [[Category: McDonough, M A.]] |
| - | [[Category: Schofield, C | + | [[Category: Schofield, C J.]] |
| - | [[Category: Sleeman, M | + | [[Category: Sleeman, M C.]] |
| - | [[Category: Sorensen, J | + | [[Category: Sorensen, J L.]] |
[[Category: ACO]] | [[Category: ACO]] | ||
[[Category: BCN]] | [[Category: BCN]] | ||
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[[Category: crotonase]] | [[Category: crotonase]] | ||
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 16:24:31 2008'' |
Revision as of 14:24, 21 February 2008
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carboxymethylproline synthase (CarB) from pectobacterium carotovora, complexed with acetyl CoA and bicine
Overview
The first step in the biosynthesis of the medicinally important carbapenem family of beta-lactam antibiotics is catalyzed by carboxymethylproline synthase (CarB), a unique member of the crotonase superfamily. CarB catalyzes formation of (2S,5S)-carboxymethylproline [(2S,5S)-t-CMP] from malonyl-CoA and l-glutamate semialdehyde. In addition to using a cosubstrate, CarB catalyzes C-C and C-N bond formation processes as well as an acyl-coenzyme A hydrolysis reaction. We describe the crystal structure of CarB in the presence and absence of acetyl-CoA at 2.24 A and 3.15 A resolution, respectively. The structures reveal that CarB contains a conserved oxy-anion hole probably required for decarboxylation of malonyl-CoA and stabilization of the resultant enolate. Comparison of the structures reveals that conformational changes (involving His(229)) in the cavity predicted to bind l-glutamate semialdehyde occur on (co)substrate binding. Mechanisms for the formation of the carboxymethylproline ring are discussed in the light of the structures and the accompanying studies using isotopically labeled substrates; cyclization via 1,4-addition is consistent with the observed labeling results (providing that hydrogen exchange at the C-6 position of carboxymethylproline does not occur). The side chain of Glu(131) appears to be positioned to be involved in hydrolysis of the carboxymethylproline-CoA ester intermediate. Labeling experiments ruled out the possibility that hydrolysis proceeds via an anhydride in which water attacks a carbonyl derived from Glu(131), as proposed for 3-hydroxyisobutyryl-CoA hydrolase. The structural work will aid in mutagenesis studies directed at altering the selectivity of CarB to provide intermediates for the production of clinically useful carbapenems.
About this Structure
2A81 is a Single protein structure of sequence from Pectobacterium carotovorum with and as ligands. Full crystallographic information is available from OCA.
Reference
Structural and mechanistic studies on carboxymethylproline synthase (CarB), a unique member of the crotonase superfamily catalyzing the first step in carbapenem biosynthesis., Sleeman MC, Sorensen JL, Batchelar ET, McDonough MA, Schofield CJ, J Biol Chem. 2005 Oct 14;280(41):34956-65. Epub 2005 Aug 11. PMID:16096274
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