'''STRUCTURAL ANALYSIS OF THE ZINC HYDROXIDE-THR 199-GLU 106 HYDROGEN BONDING NETWORK IN HUMAN CARBONIC ANHYDRASE II'''
===STRUCTURAL ANALYSIS OF THE ZINC HYDROXIDE-THR 199-GLU 106 HYDROGEN BONDING NETWORK IN HUMAN CARBONIC ANHYDRASE II===
==Overview==
<!--
The significance of the zinc hydroxide-Thr-199-Glu-106 hydrogen-bond network in the active site of human carbonic anhydrase II has been examined by X-ray crystallographic analyses of site-specific mutants. Mutants with Ala-199 and Ala-106 or Gln-106 have low catalytic activities, while a mutant with Asp-106 has almost full CO2 hydration activity. The structures of these four mutants, as well as that of the bicarbonate complex of the mutant with Ala-199, have been determined at 1.7 to 2.2 A resolution. Removal of the gamma atoms of residue 199 leads to a distorted tetrahedral geometry at the zinc ion, and a catalytically important zinc-bound water molecule has moved towards Glu-106. In the bicarbonate complex of the mutant with Ala-199 one oxygen atom from bicarbonate binds to zinc without displacing this water molecule. Tetrahedral coordination geometries are retained in the mutants at position 106. The mutants with Ala-106 and Gln-106 have a zinc-bound sulfate ion, whereas this sulfate site is only partially occupied in the mutant with Asp-106. The hydrogen-bond network seems to be "reversed" in the mutants with Ala-106 and Gln-106. The network is preserved as in native enzyme in the mutant with Asp-106 but the side chain of Asp-106 is more extended than that of Glu-106 in the native enzyme. These results illustrate the importance of Glu-106 and Thr-199 for controlling the precise coordination geometry of the zinc ion and its ligand preferences which results in an optimal orientation of a zinc-bound hydroxide ion for an attack on the CO2 substrate.
The line below this paragraph, {{ABSTRACT_PUBMED_7901850}}, adds the Publication Abstract to the page
(as it appears on PubMed at http://www.pubmed.gov), where 7901850 is the PubMed ID number.
-->
{{ABSTRACT_PUBMED_7901850}}
==About this Structure==
==About this Structure==
Line 27:
Line 31:
[[Category: Lindskog, S.]]
[[Category: Lindskog, S.]]
[[Category: Xue, Y.]]
[[Category: Xue, Y.]]
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 12:31:43 2008''
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 20:28:48 2008''
Revision as of 17:28, 30 June 2008
This article has been automatically seeded. Changes to this page should pertain to the PDB entry only and not to the protein or biomolecule in general.
1CAL is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.
Reference
Structural analysis of the zinc hydroxide-Thr-199-Glu-106 hydrogen-bond network in human carbonic anhydrase II., Xue Y, Liljas A, Jonsson BH, Lindskog S, Proteins. 1993 Sep;17(1):93-106. PMID:7901850
