1heb: Difference between revisions
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|PDB= 1heb |SIZE=350|CAPTION= <scene name='initialview01'>1heb</scene>, resolution 2.0Å | |PDB= 1heb |SIZE=350|CAPTION= <scene name='initialview01'>1heb</scene>, resolution 2.0Å | ||
|SITE= | |SITE= | ||
|LIGAND= <scene name='pdbligand= | |LIGAND= <scene name='pdbligand=HG:MERCURY+(II)+ION'>HG</scene>, <scene name='pdbligand=ZN:ZINC+ION'>ZN</scene> | ||
|ACTIVITY= [http://en.wikipedia.org/wiki/Carbonate_dehydratase Carbonate dehydratase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=4.2.1.1 4.2.1.1] | |ACTIVITY= <span class='plainlinks'>[http://en.wikipedia.org/wiki/Carbonate_dehydratase Carbonate dehydratase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=4.2.1.1 4.2.1.1] </span> | ||
|GENE= | |GENE= | ||
|DOMAIN= | |||
|RELATEDENTRY= | |||
|RESOURCES=<span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1heb FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1heb OCA], [http://www.ebi.ac.uk/pdbsum/1heb PDBsum], [http://www.rcsb.org/pdb/explore.do?structureId=1heb RCSB]</span> | |||
}} | }} | ||
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==Overview== | ==Overview== | ||
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 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) | ||
==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.]] | ||
[[Category: lyase(oxo-acid)]] | [[Category: lyase(oxo-acid)]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Mar 30 21:03:21 2008'' | ||
