View source for 1hcb

[[Image:1hcb.gif|left|200px]]<br />
<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.

==About this Structure==
1HCB 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]. 

==Reference==
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:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=8057362 8057362]
[[Category: Carbonate dehydratase]]
[[Category: Homo sapiens]]
[[Category: Single protein]]
[[Category: Kannan, K.K.]]
[[Category: Kumar, V.]]
[[Category: BCT]]
[[Category: ZN]]
[[Category: lyase(oxo-acid)]]

''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Mon Nov 12 17:15:33 2007''