Linked Life Data

16106378

Source:http://linkedlifedata.com/resource/pubmed/id/16106378

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
2005-9-26
pubmed:abstractText
Human carbonic anhydrase II (HCA II) has a histidine at position 64 (His64) that donates a proton to the zinc-bound hydroxide in catalysis of the dehydration of bicarbonate. To examine the effect of the histidine location on proton shuttling, His64 was replaced with Ala and Thr200 replaced with histidine (H64A-T200H HCAII), effectively relocating the proton shuttle residue 2 A closer to the zinc-bound hydroxide compared to wild type HCA II. The crystal structure of H64A-T200H HCA II at 1.8 A resolution shows the side chain of His200 directly hydrogen-bonded with the zinc-bound solvent. Different proton transfer processes were observed at pH 6 and at pH 8 during the catalytic hydration-dehydration cycle, measured by mass spectrometry as the depletion of 18O from C18O2 by H64A-T200H HCA II. The process at pH 6.0 is attributed to proton transfer between the side chain of His200 and the zinc-bound hydroxide, in analogy with proton transfer involving His64 in wild-type HCA II. At pH 8.0 it is attributed to proton transfer between bicarbonate and the zinc-bound hydroxide, as supported by the dependence of the rate of proton transfer on bicarbonate concentration and on solvent hydrogen isotope effects. This study establishes that a histidine directly hydrogen-bonded to the zinc-bound hydroxide, can adopt the correct distance geometry to support proton transfer
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Nov
pubmed:issn
1097-0134
pubmed:author
pubmed:copyrightInfo
Copyright 2005 Wiley-Liss, Inc.
pubmed:issnType
Electronic
pubmed:day
1
pubmed:volume
61
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
239-45
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
2005
pubmed:articleTitle
Proton transfer in a Thr200His mutant of human carbonic anhydrase II.
pubmed:affiliation
Department of Pharmacology and Therapeutics University of Florida, Gainesville, Florida 32610-0245, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, N.I.H., Extramural