1hcb: Difference between revisions

Revision as of 13:59, 21 February 2008

ENZYME-SUBSTRATE INTERACTIONS: STRUCTURE OF HUMAN CARBONIC ANHYDRASE I COMPLEXED WITH BICARBONATE

OverviewOverview

The structure of HCAI-HCO3- complex has been refined with 10-1.6A X-ray diffraction data to an R-value of 17.7%. The structure reveals monodentate binding of the HCO3- anion at an apical tetrahedral position to the zinc ion. The binding mode and interactions of HCO3- in HCAI differ from that in HCAII. The activity linked H2O/OH- group in the free HCAI is replaced by the hydroxyl group of the bicarbonate anion. This result rules out the rearrangement of the bound HCO3- advocated earlier to explain the microscopic reversibility of the catalysed reaction. From the geometry of the H-bonds between Glu106-Thr199 pair and Glu117-His119 couple, the glutamic acids are expected to be ionized and accept H-bonds from their partners. The product-inhibiton by HCO3- anion is explained on the basis of proton localization on His119 in the Glu117-His119 couple. These results are consistent with the hypothesis that Glu117-His119 tunes the ionicity of the Zn2+ and the binding strength of HCO3- anion. A pi hydrogen bond is observed between a water and phenyl ring of the Tyr114 residue.

About this StructureAbout this Structure

1HCB 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.

ReferenceReference

Enzyme-substrate interactions. Structure of human carbonic anhydrase I complexed with bicarbonate., Kumar V, Kannan KK, J Mol Biol. 1994 Aug 12;241(2):226-32. PMID:8057362

Page seeded by OCA on Thu Feb 21 12:59:44 2008

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OCA

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-[[Image:1hcb.gif|left|200px]]<br />
+[[Image:1hcb.gif|left|200px]]<br /><applet load="1hcb" size="350" color="white" frame="true" align="right" spinBox="true"
-<applet load="1hcb" size="450" color="white" frame="true" align="right" spinBox="true"
 caption="1hcb, resolution 1.6&Aring;" />
 '''ENZYME-SUBSTRATE INTERACTIONS: STRUCTURE OF HUMAN CARBONIC ANHYDRASE I COMPLEXED WITH BICARBONATE'''<br />
 ==Overview==
-The structure of HCAI-HCO3- complex has been refined with 10-1.6A X-ray, diffraction data to an R-value of 17.7%. The structure reveals monodentate, binding of the HCO3- anion at an apical tetrahedral position to the zinc, ion. The binding mode and interactions of HCO3- in HCAI differ from that, in HCAII. The activity linked H2O/OH- group in the free HCAI is replaced, by the hydroxyl group of the bicarbonate anion. This result rules out the, rearrangement of the bound HCO3- advocated earlier to explain the, microscopic reversibility of the catalysed reaction. From the geometry of, the H-bonds between Glu106-Thr199 pair and Glu117-His119 couple, the, glutamic acids are expected to be ionized and accept H-bonds from their, partners. The product-inhibiton by HCO3- anion is explained on the basis, of proton localization on His119 in the Glu117-His119 couple. These, results are consistent with the hypothesis that Glu117-His119 tunes the, ionicity of the Zn2+ and the binding strength of HCO3- anion. A pi, hydrogen bond is observed between a water and phenyl ring of the Tyr114, residue.
+The structure of HCAI-HCO3- complex has been refined with 10-1.6A X-ray diffraction data to an R-value of 17.7%. The structure reveals monodentate binding of the HCO3- anion at an apical tetrahedral position to the zinc ion. The binding mode and interactions of HCO3- in HCAI differ from that in HCAII. The activity linked H2O/OH- group in the free HCAI is replaced by the hydroxyl group of the bicarbonate anion. This result rules out the rearrangement of the bound HCO3- advocated earlier to explain the microscopic reversibility of the catalysed reaction. From the geometry of the H-bonds between Glu106-Thr199 pair and Glu117-His119 couple, the glutamic acids are expected to be ionized and accept H-bonds from their partners. The product-inhibiton by HCO3- anion is explained on the basis of proton localization on His119 in the Glu117-His119 couple. These results are consistent with the hypothesis that Glu117-His119 tunes the ionicity of the Zn2+ and the binding strength of HCO3- anion. A pi hydrogen bond is observed between a water and phenyl ring of the Tyr114 residue.
 ==About this Structure==
-HCB 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 BCT 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://ispc.weizmann.ac.il/oca-bin/ocashort?id=1HCB OCA].
+HCB 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=BCT:'>BCT</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=1HCB OCA].
 ==Reference==
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 [[Category: Homo sapiens]]
 [[Category: Single protein]]
-[[Category: Kannan, K.K.]]
+[[Category: Kannan, K K.]]
 [[Category: Kumar, V.]]
 [[Category: BCT]]
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 [[Category: lyase(oxo-acid)]]
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