12ca
From Proteopedia
(New page: 200px<br /> <applet load="12ca" size="450" color="white" frame="true" align="right" spinBox="true" caption="12ca, resolution 2.4Å" /> '''ALTERING THE MOUTH O...) |
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| - | [[Image:12ca.gif|left|200px]]<br /> | + | [[Image:12ca.gif|left|200px]]<br /><applet load="12ca" size="350" color="white" frame="true" align="right" spinBox="true" |
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caption="12ca, resolution 2.4Å" /> | caption="12ca, resolution 2.4Å" /> | ||
'''ALTERING THE MOUTH OF A HYDROPHOBIC POCKET. STRUCTURE AND KINETICS OF HUMAN CARBONIC ANHYDRASE II MUTANTS AT RESIDUE VAL-121'''<br /> | '''ALTERING THE MOUTH OF A HYDROPHOBIC POCKET. STRUCTURE AND KINETICS OF HUMAN CARBONIC ANHYDRASE II MUTANTS AT RESIDUE VAL-121'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Eleven amino acid substitutions at Val-121 of human carbonic anhydrase II | + | Eleven amino acid substitutions at Val-121 of human carbonic anhydrase II including Gly, Ala, Ser, Leu, Ile, Lys, and Arg, were constructed by site-directed mutagenesis. This residue is at the mouth of the hydrophobic pocket in the enzyme active site. The CO2 hydrase activity and the p-nitrophenyl esterase activity of these CAII variants correlate with the hydrophobicity of the residue, suggesting that the hydrophobic character of this residue is important for catalysis. The effects of these mutations on the steady-state kinetics for CO2 hydration occur mainly in kcat/Km and Km, consistent with involvement of this residue in CO2 association. The Val-121----Ala mutant, which exhibits about one-third normal CO2 hydrase activity, has been studied by x-ray crystallographic methods. No significant changes in the mutant enzyme conformation are evident relative to the wild-type enzyme. Since Val-121 is at the mouth of the hydrophobic pocket, its substitution by the methyl side chain of alanine makes the pocket mouth significantly wider than that of the wild-type enzyme. Hence, although a moderately wide (and deep) pocket is important for substrate association, a wider mouth to this pocket does not seriously compromise the catalytic approach of CO2 toward nucleophilic zinc-bound hydroxide. |
==Disease== | ==Disease== | ||
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==About this Structure== | ==About this Structure== | ||
| - | 12CA is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with ZN and HG as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [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] Full crystallographic information is available from [http:// | + | 12CA is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with <scene name='pdbligand=ZN:'>ZN</scene> and <scene name='pdbligand=HG:'>HG</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [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] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=12CA OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Homo sapiens]] | [[Category: Homo sapiens]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Christianson, D | + | [[Category: Christianson, D W.]] |
| - | [[Category: Nair, S | + | [[Category: Nair, S K.]] |
[[Category: HG]] | [[Category: HG]] | ||
[[Category: ZN]] | [[Category: ZN]] | ||
[[Category: lyase(oxo-acid)]] | [[Category: lyase(oxo-acid)]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 11:37:57 2008'' |
Revision as of 09:37, 21 February 2008
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ALTERING THE MOUTH OF A HYDROPHOBIC POCKET. STRUCTURE AND KINETICS OF HUMAN CARBONIC ANHYDRASE II MUTANTS AT RESIDUE VAL-121
Contents |
Overview
Eleven amino acid substitutions at Val-121 of human carbonic anhydrase II including Gly, Ala, Ser, Leu, Ile, Lys, and Arg, were constructed by site-directed mutagenesis. This residue is at the mouth of the hydrophobic pocket in the enzyme active site. The CO2 hydrase activity and the p-nitrophenyl esterase activity of these CAII variants correlate with the hydrophobicity of the residue, suggesting that the hydrophobic character of this residue is important for catalysis. The effects of these mutations on the steady-state kinetics for CO2 hydration occur mainly in kcat/Km and Km, consistent with involvement of this residue in CO2 association. The Val-121----Ala mutant, which exhibits about one-third normal CO2 hydrase activity, has been studied by x-ray crystallographic methods. No significant changes in the mutant enzyme conformation are evident relative to the wild-type enzyme. Since Val-121 is at the mouth of the hydrophobic pocket, its substitution by the methyl side chain of alanine makes the pocket mouth significantly wider than that of the wild-type enzyme. Hence, although a moderately wide (and deep) pocket is important for substrate association, a wider mouth to this pocket does not seriously compromise the catalytic approach of CO2 toward nucleophilic zinc-bound hydroxide.
Disease
Known disease associated with this structure: Osteopetrosis, autosomal recessive 3, with renal tubular acidosis OMIM:[611492]
About this Structure
12CA is a Single protein structure of sequence from Homo sapiens with and as ligands. Active as Carbonate dehydratase, with EC number 4.2.1.1 Full crystallographic information is available from OCA.
Reference
Altering the mouth of a hydrophobic pocket. Structure and kinetics of human carbonic anhydrase II mutants at residue Val-121., Nair SK, Calderone TL, Christianson DW, Fierke CA, J Biol Chem. 1991 Sep 15;266(26):17320-5. PMID:1910042
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