PDBsum entry 1hcb

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Lyase(oxo-acid) PDB id
Protein chain
258 a.a.
Waters ×254

References listed in PDB file
Key reference
Title Enzyme-Substrate interactions. Structure of human carbonic anhydrase i complexed with bicarbonate.
Authors V.Kumar, K.K.Kannan.
Ref. J Mol Biol, 1994, 241, 226-232.
PubMed id 8057362
Note In the PDB file this reference is annotated as "TO BE PUBLISHED". The citation details given above were identified by an automated search of PubMed on title and author names, giving a perfect match.
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.
Secondary reference #1
Title Structure of human carbonic anhydrase i complexed with gold cyanide inhibitor: inhibition mechanism
Authors V.Kumar, K.K.Kannan.
Ref. acta crystallogr ,sect a, 1993, 49, 92.
Secondary reference #2
Title Human carbonic anhydrase i - Iodide complex: structure and inhibition mechanism
Authors V.Kumar, P.Satyamurthy, K.K.Kannan.
Ref. acta crystallogr ,sect a, 1987, 43, .
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