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| [[Image:1hcb.gif|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_1hcb| PDB=1hcb | SCENE= }} | | {{STRUCTURE_1hcb| PDB=1hcb | SCENE= }} |
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| '''ENZYME-SUBSTRATE INTERACTIONS: STRUCTURE OF HUMAN CARBONIC ANHYDRASE I COMPLEXED WITH BICARBONATE'''
| | ===ENZYME-SUBSTRATE INTERACTIONS: STRUCTURE OF HUMAN CARBONIC ANHYDRASE I COMPLEXED WITH BICARBONATE=== |
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| ==Overview==
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| 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 line below this paragraph, {{ABSTRACT_PUBMED_8057362}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 8057362 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_8057362}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Kannan, K K.]] | | [[Category: Kannan, K K.]] |
| [[Category: Kumar, V.]] | | [[Category: Kumar, V.]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 18:41:28 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 07:58:41 2008'' |
