1g0e
From Proteopedia
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'''SITE-SPECIFIC MUTANT (HIS64 REPLACED WITH ALA) OF HUMAN CARBONIC ANHYDRASE II COMPLEXED WITH 4-METHYLIMIDAZOLE''' | '''SITE-SPECIFIC MUTANT (HIS64 REPLACED WITH ALA) OF HUMAN CARBONIC ANHYDRASE II COMPLEXED WITH 4-METHYLIMIDAZOLE''' | ||
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[[Category: McKenna, R.]] | [[Category: McKenna, R.]] | ||
[[Category: 4-methylimidazole]] | [[Category: 4-methylimidazole]] | ||
| - | [[Category: | + | [[Category: Chemical rescue]] |
| - | [[Category: | + | [[Category: Twisted beta sheet]] |
| - | [[Category: | + | [[Category: Zinc metalloenzyme,protein ligand complex]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 16:58:23 2008'' | |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 13:58, 2 May 2008
SITE-SPECIFIC MUTANT (HIS64 REPLACED WITH ALA) OF HUMAN CARBONIC ANHYDRASE II COMPLEXED WITH 4-METHYLIMIDAZOLE
Overview
Histidine 64 in human carbonic anhydrase II (HCA II) functions in the catalytic pathway of CO(2) hydration as a shuttle to transfer protons between the zinc-bound water and bulk water. Catalysis of the exchange of (18)O between CO(2) and water, measured by mass spectrometry, is dependent on this proton transfer and was decreased more than 10-fold for H64A HCA II compared with wild-type HCA II. The loss of catalytic activity of H64A HCA II could be rescued by 4-methylimidazole (4-MI), an exogenous proton donor, in a saturable process with a maximum activity of 40% of wild-type HCA II. The crystal structure of the rescued complex at 1.6 A resolution shows 4-MI bound in the active-site cavity of H64A HCA II, through pi stacking interactions with Trp 5 and H-bonding interactions with water molecules. In this location, 4-MI is about 12 A from the zinc and approximates the observed "out" position of His 64 in the structure of the wild-type enzyme. 4-MI appears to compensate for the absence of His 64 and rescues the catalytic activity of the H64A HCA II mutant. This result strongly suggests that the out conformation of His 64 is effective in the transfer of protons between the zinc-bound solvent molecule and solution.
About this Structure
1G0E is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.
Reference
Structural and kinetic analysis of the chemical rescue of the proton transfer function of carbonic anhydrase II., Duda D, Tu C, Qian M, Laipis P, Agbandje-McKenna M, Silverman DN, McKenna R, Biochemistry. 2001 Feb 13;40(6):1741-8. PMID:11327835 Page seeded by OCA on Fri May 2 16:58:23 2008
