1xjw: Difference between revisions
No edit summary |
No edit summary |
||
| Line 1: | Line 1: | ||
[[Image:1xjw.gif|left|200px]] | [[Image:1xjw.gif|left|200px]] | ||
'''The Structure of E. coli Aspartate Transcarbamoylase Q137A Mutant in The R-State''' | {{Structure | ||
|PDB= 1xjw |SIZE=350|CAPTION= <scene name='initialview01'>1xjw</scene>, resolution 2.71Å | |||
|SITE= | |||
|LIGAND= <scene name='pdbligand=ZN:ZINC+ION'>ZN</scene> and <scene name='pdbligand=PAL:N-(PHOSPHONACETYL)-L-ASPARTIC ACID'>PAL</scene> | |||
|ACTIVITY= [http://en.wikipedia.org/wiki/Aspartate_carbamoyltransferase Aspartate carbamoyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.1.3.2 2.1.3.2] | |||
|GENE= pyrB ([http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&srchmode=5&id=562 Escherichia coli]), pyrI ([http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&srchmode=5&id=562 Escherichia coli]) | |||
}} | |||
'''The Structure of E. coli Aspartate Transcarbamoylase Q137A Mutant in The R-State''' | |||
==Overview== | ==Overview== | ||
| Line 7: | Line 16: | ||
==About this Structure== | ==About this Structure== | ||
1XJW is a [ | 1XJW is a [[Protein complex]] structure of sequences from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1XJW OCA]. | ||
==Reference== | ==Reference== | ||
A single amino acid substitution in the active site of Escherichia coli aspartate transcarbamoylase prevents the allosteric transition., Stieglitz KA, Pastra-Landis SC, Xia J, Tsuruta H, Kantrowitz ER, J Mol Biol. 2005 Jun 3;349(2):413-23. Epub 2005 Apr 9. PMID:[http:// | A single amino acid substitution in the active site of Escherichia coli aspartate transcarbamoylase prevents the allosteric transition., Stieglitz KA, Pastra-Landis SC, Xia J, Tsuruta H, Kantrowitz ER, J Mol Biol. 2005 Jun 3;349(2):413-23. Epub 2005 Apr 9. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/15890205 15890205] | ||
[[Category: Aspartate carbamoyltransferase]] | [[Category: Aspartate carbamoyltransferase]] | ||
[[Category: Escherichia coli]] | [[Category: Escherichia coli]] | ||
| Line 24: | Line 33: | ||
[[Category: allosteric enzyme]] | [[Category: allosteric enzyme]] | ||
[[Category: domain closure]] | [[Category: domain closure]] | ||
[[Category: | [[Category: electrostatic]] | ||
[[Category: intersubunit | [[Category: intersubunit interaction]] | ||
[[Category: polar | [[Category: polar contact]] | ||
[[Category: small angle x-ray scattering]] | [[Category: small angle x-ray scattering]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Mar 20 15:10:45 2008'' | ||
Revision as of 16:10, 20 March 2008
| |||||||
| , resolution 2.71Å | |||||||
|---|---|---|---|---|---|---|---|
| Ligands: | and | ||||||
| Gene: | pyrB (Escherichia coli), pyrI (Escherichia coli) | ||||||
| Activity: | Aspartate carbamoyltransferase, with EC number 2.1.3.2 | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
The Structure of E. coli Aspartate Transcarbamoylase Q137A Mutant in The R-State
OverviewOverview
Modeling of the tetrahedral intermediate within the active site of Escherichia coli aspartate transcarbamoylase revealed a specific interaction with the side-chain of Gln137, an interaction not previously observed in the structure of the X-ray enzyme in the presence of N-phosphonacetyl-L-aspartate (PALA). Previous site-specific mutagenesis experiments showed that when Gln137 was replaced by alanine, the resulting mutant enzyme (Q137A) exhibited approximately 50-fold less activity than the wild-type enzyme, exhibited no homotropic cooperativity, and the binding of both carbamoyl phosphate and aspartate were extremely compromised. To elucidate the structural alterations in the mutant enzyme that might lead to such pronounced changes in kinetic and binding properties, the Q137A enzyme was studied by time-resolved, small-angle X-ray scattering and its structure was determined in the presence of PALA to 2.7 angstroms resolution. Time-resolved, small-angle X-ray scattering established that the natural substrates, carbamoyl phosphate and L-aspartate, do not induce in the Q137A enzyme the same conformational changes as observed for the wild-type enzyme, although the scattering pattern of the Q137A and wild-type enzymes in the presence of PALA were identical. The overall structure of the Q137A enzyme is similar to that of the R-state structure of wild-type enzyme with PALA bound. However, there are differences in the manner by which the Q137A enzyme coordinates PALA, especially in the side-chain positions of Arg105 and His134. The replacement of Gln137 by Ala also has a dramatic effect on the electrostatics of the active site. These data taken together suggest that the side-chain of Gln137 in the wild-type enzyme is required for the binding of carbamoyl phosphate in the proper orientation so as to induce conformational changes required for the creation of the high-affinity aspartate-binding site. The inability of carbamoyl phosphate to create the high-affinity binding site in the Q137A enzyme results in an enzyme locked in the low-activity low-affinity T state. These results emphasize the absolute requirement of the binding of carbamoyl phosphate for the creation of the high-affinity aspartate-binding site and for inducing the homotropic cooperativity in aspartate transcarbamoylase.
About this StructureAbout this Structure
1XJW is a Protein complex structure of sequences from Escherichia coli. Full crystallographic information is available from OCA.
ReferenceReference
A single amino acid substitution in the active site of Escherichia coli aspartate transcarbamoylase prevents the allosteric transition., Stieglitz KA, Pastra-Landis SC, Xia J, Tsuruta H, Kantrowitz ER, J Mol Biol. 2005 Jun 3;349(2):413-23. Epub 2005 Apr 9. PMID:15890205
Page seeded by OCA on Thu Mar 20 15:10:45 2008