1hcb
From Proteopedia
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| , resolution 1.6Å | |||||||
|---|---|---|---|---|---|---|---|
| Ligands: | , | ||||||
| Activity: | Carbonate dehydratase, with EC number 4.2.1.1 | ||||||
| Resources: | FirstGlance, OCA, PDBsum, RCSB | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
ENZYME-SUBSTRATE INTERACTIONS: STRUCTURE OF HUMAN CARBONIC ANHYDRASE I COMPLEXED WITH BICARBONATE
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 Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from 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:8057362
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