|
|
| Line 1: |
Line 1: |
| [[Image:1gqt.jpg|left|200px]] | | {{Seed}} |
| | [[Image:1gqt.png|left|200px]] |
|
| |
|
| <!-- | | <!-- |
| Line 9: |
Line 10: |
| {{STRUCTURE_1gqt| PDB=1gqt | SCENE= }} | | {{STRUCTURE_1gqt| PDB=1gqt | SCENE= }} |
|
| |
|
| '''ACTIVATION OF RIBOKINASE BY MONOVALENT CATIONS'''
| | ===ACTIVATION OF RIBOKINASE BY MONOVALENT CATIONS=== |
|
| |
|
|
| |
|
| ==Overview==
| | <!-- |
| Carbohydrate kinases frequently require a monovalent cation for their activity. The physical basis of this phenomenon is, however, usually unclear. We report here that Escherichia coli ribokinase is activated by potassium with an apparent K(d) of 5 mM; the enzyme should therefore be fully activated under physiological conditions. Cesium can be used as an alternative ion, with an apparent K(d) of 17 mM. An X-ray structure of ribokinase in the presence of cesium was solved and refined at 2.34 A resolution. The cesium ion was bound between two loops immediately adjacent to the anion hole of the active site. The buried location of the site suggests that conformational changes will accompany ion binding, thus providing a direct mechanism for activation. Comparison with structures of a related enzyme, the adenosine kinase of Toxoplasma gondii, support this proposal. This is apparently the first instance in which conformational activation of a carbohydrate kinase by a monovalent cation has been assigned a clear structural basis. The mechanism is probably general to ribokinases, to some adenosine kinases, and to other members of the larger family. A careful re-evaluation of the biochemical and structural data is suggested for other enzyme systems.
| | The line below this paragraph, {{ABSTRACT_PUBMED_11786021}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 11786021 is the PubMed ID number. |
| | --> |
| | {{ABSTRACT_PUBMED_11786021}} |
|
| |
|
| ==About this Structure== | | ==About this Structure== |
| Line 31: |
Line 35: |
| [[Category: Ribose]] | | [[Category: Ribose]] |
| [[Category: Transferase]] | | [[Category: Transferase]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 17:54:24 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 05:55:13 2008'' |