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| [[Image:1hea.jpg|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_1hea| PDB=1hea | SCENE= }} | | {{STRUCTURE_1hea| PDB=1hea | SCENE= }} |
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| '''CARBONIC ANHYDRASE II (CARBONATE DEHYDRATASE) (HCA II) (E.C.4.2.1.1) MUTANT WITH LEU 198 REPLACED BY ARG (L198R)'''
| | ===CARBONIC ANHYDRASE II (CARBONATE DEHYDRATASE) (HCA II) (E.C.4.2.1.1) MUTANT WITH LEU 198 REPLACED BY ARG (L198R)=== |
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| ==Overview==
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| The three-dimensional structures of Leu-198-->Glu, Leu-198-->His, Leu-198-->Arg, and Leu-198-->Ala variants of human carbonic anhydrase II (CAII) have each been determined by X-ray crystallographic methods to a resolution of 2.0 A. The side chain of Leu-198 is located at the mouth of the active site hydrophobic pocket, and this pocket is required for substrate association. Hydrophobic-->hydrophilic amino acid substitutions at the mouth of the pocket decrease kcat/KM for CO2 hydration: the CO2 hydrase activities of Leu-198-->Glu, Leu-198-->His, and Leu-198-->Arg CAIIs are diminished 19-fold, 10-fold, and 17-fold, respectively, relative to the wild-type enzyme; however, the substitution of a compact aliphatic side chain for Leu-198 has a smaller effect on catalysis, in that Leu-198-->Ala CAII exhibits only a 3-fold decrease in CO2 hydrase activity [Krebs, J. F., Rana, F., Dluhy, R. A., & Fierke, C. A. (1993) Biochemistry (preceding paper in this issue)]. It is intriguing that CO2 hydrase activity is not severely diminished in Leu-198-->Arg CAII, even though the side chain of Arg-198 blocks the hydrophobic pocket. Therefore, the bulky side chain of Arg-198 must be reasonably mobile in order to accommodate substrate association. Significantly, a residue larger than the wild-type Leu-198 side chain does not necessarily block the substrate association pocket; e.g., the side chain of Glu-198 packs against a hydrophobic patch, the net result of which is a wider mouth for the pocket.(ABSTRACT TRUNCATED AT 250 WORDS)
| | The line below this paragraph, {{ABSTRACT_PUBMED_8485129}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 8485129 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_8485129}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Christianson, D W.]] | | [[Category: Christianson, D W.]] |
| [[Category: Nair, S K.]] | | [[Category: Nair, S K.]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 18:45:31 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 08:04:05 2008'' |
