Linked Life Data

10222206

Source:http://linkedlifedata.com/resource/pubmed/id/10222206

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
5
pubmed:dateCreated
1999-5-19
pubmed:abstractText
The crystallographic structures of several copper-containing nitrite reductases are now available. Despite this wealth of structural data, no definitive information is available as to whether the reaction proceeds by an ordered mechanism where nitrite binds to the oxidised type 2 site, followed by an internal electron transfer from the type 1 Cu, or whether binding occurs to the reduced type 2 Cu centre, or a random mechanism operates. We present here the first structural information on both types of Cu centres for the reduced form of NiR from Alcaligenes xylosoxidans (AxNiR) using X-ray absorption spectroscopy. The reduced type 2 Cu site EXAFS shows striking similarity to the EXAFS data for reduced bovine superoxide dismutase (Cu2Zn2 SOD), providing strong evidence for the loss of the water molecule from the catalytic Cu site in NiR on reduction resulting in a tri-coordinate Cu site similar to that in Cu2Zn2 SOD. The reduced type 2 Cu site of AxNiR is shown to be unable to bind inhibitory ligands such as azide, and to react very sluggishly with nitrite leading to only a slow re-oxidation of the the type 1 centre. These observations provide strong evidence that turnover of AxNiR proceeds by an ordered mechanism in which nitrite binds to the oxidised type 2 Cu centres before electron transfer from the reduced type 1 centre occurs. We propose that the two links between the Cu sites of AxNiR, namely His129-Cys130 and His89-Asp92-His94 are utilised for electron transfer and for communicating the status of the type 2 Cu site, respectively. Nitrite binding at type 2 Cu is sensed by the proton abstracting group Asp92 and the type 2 Cu ligand His94, and relayed to the type 1 Cu site via His89 thus triggering an internal electron transfer. The similarity of the type 2 Cu NiR catalytic site to the reduced Cu site of SOD is examined in some detail together with the biochemical evidence for the SOD activity of AxNiR.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0022-2836
pubmed:author
pubmed:copyrightInfo
Copyright 1999 Academic Press.
pubmed:issnType
Print
pubmed:day
16
pubmed:volume
287
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1001-9
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1999
pubmed:articleTitle
Structural and kinetic evidence for an ordered mechanism of copper nitrite reductase.
pubmed:affiliation
CCLRC Daresbury Laboratory, Warrington, Cheshire, WA4 4AD, UK.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, Non-U.S. Gov't