2nsl
From Proteopedia
(New page: 200px<br /><applet load="2nsl" size="450" color="white" frame="true" align="right" spinBox="true" caption="2nsl, resolution 2.00Å" /> '''E. coli PurE H45N mu...) |
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| - | [[Image:2nsl.gif|left|200px]]<br /><applet load="2nsl" size=" | + | [[Image:2nsl.gif|left|200px]]<br /><applet load="2nsl" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="2nsl, resolution 2.00Å" /> | caption="2nsl, resolution 2.00Å" /> | ||
'''E. coli PurE H45N mutant complexed with CAIR'''<br /> | '''E. coli PurE H45N mutant complexed with CAIR'''<br /> | ||
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==About this Structure== | ==About this Structure== | ||
| - | 2NSL is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with C2R as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Phosphoribosylaminoimidazole_carboxylase Phosphoribosylaminoimidazole carboxylase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=4.1.1.21 4.1.1.21] Full crystallographic information is available from [http:// | + | 2NSL is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with <scene name='pdbligand=C2R:'>C2R</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Phosphoribosylaminoimidazole_carboxylase Phosphoribosylaminoimidazole carboxylase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=4.1.1.21 4.1.1.21] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2NSL OCA]. |
==Reference== | ==Reference== | ||
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[[Category: kinked c-terminal helix]] | [[Category: kinked c-terminal helix]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Wed Jan 23 15:35:25 2008'' |
Revision as of 13:35, 23 January 2008
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E. coli PurE H45N mutant complexed with CAIR
Overview
N5-Carboxyaminoimidazole ribonucleotide mutase (N5-CAIR mutase or PurE), from Escherichia coli catalyzes the reversible interconversion of N5-CAIR, to carboxyaminoimidazole ribonucleotide (CAIR) with direct CO2 transfer., Site-directed mutagenesis, a pH-rate profile, DFT calculations, and X-ray, crystallography together provide new insight into the mechanism of this, unusual transformation. These studies suggest that a conserved, protonated, histidine (His45) plays an essential role in catalysis. The importance of, proton transfers is supported by DFT calculations on CAIR and N5-CAIR, analogues in which the ribose 5'-phosphate is replaced with a methyl, group. The calculations suggest that the nonaromatic tautomer of CAIR, (isoCAIR) is only 3.1 kcal/mol higher in energy than its aromatic, counterpart, implicating this species as a potential intermediate in the, PurE-catalyzed reaction. A structure of wild-type PurE cocrystallized with, 4-nitroaminoimidazole ribonucleotide (NO2-AIR, a CAIR analogue) and, structures of H45N and H45Q PurEs soaked with CAIR have been determined, and provide the first insight into the binding of an intact PurE, substrate. A comparison of 19 available structures of PurE and PurE, mutants in apo and nucleotide-bound forms reveals a common, buried, carboxylate or CO2 binding site for CAIR and N5-CAIR in a hydrophobic, pocket in which the carboxylate or CO2 interacts with backbone amides., This work has led to a mechanistic proposal in which the carboxylate, orients the substrate for proton transfer from His45 to N5-CAIR to form an, enzyme-bound aminoimidazole ribonucleotide (AIR) and CO2 intermediate., Subsequent movement of the aminoimidazole moiety of AIR reorients it for, addition of CO2 at C4 to generate isoCAIR. His45 is now in a position to, remove a C4 proton to produce CAIR.
About this Structure
2NSL is a Single protein structure of sequence from Escherichia coli with as ligand. Active as Phosphoribosylaminoimidazole carboxylase, with EC number 4.1.1.21 Full crystallographic information is available from OCA.
Reference
N5-CAIR mutase: role of a CO2 binding site and substrate movement in catalysis., Hoskins AA, Morar M, Kappock TJ, Mathews II, Zaugg JB, Barder TE, Peng P, Okamoto A, Ealick SE, Stubbe J, Biochemistry. 2007 Mar 13;46(10):2842-55. Epub 2007 Feb 14. PMID:17298082
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