Linked Life Data

15984889

Source:http://linkedlifedata.com/resource/pubmed/id/15984889

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
26
pubmed:dateCreated
2005-6-29
pubmed:abstractText
Light regulation of enzyme activities in oxygenic photosynthesis is mediated by ferredoxin:thioredoxin reductase (FTR), a novel class of disulfide reductase with an active site comprising a [Fe(4)S(4)](2+) cluster and an adjacent disulfide, that catalyzes reduction of the thioredoxin disulfide in two sequential one-electron steps using a [Fe(2)S(2)](2+/+) ferredoxin as the electron donor. In this work, we report on spectroscopic (EPR, VTMCD, resonance Raman, and Mössbauer) and redox characterization of the active site of FTR in various forms of the enzyme, including wild-type FTR, point-mutation variants at each of the active-site cysteine residues, and stable analogues of the one-electron-reduced FTR-Trx heterodisulfide intermediate. The results reveal novel site-specific Fe(4)S(4)-cluster chemistry in oxidized, one-electron-reduced, and two-electron-reduced forms of FTR. In the resting enzyme, a weak interaction between the Fe(4)S(4) cluster and the active-site disulfide promotes charge buildup at a unique Fe site and primes the active site to accept an electron from ferredoxin to break the disulfide bond. In one-electron-reduced analogues, cleavage of the active-site disulfide is accompanied by coordination of one of the cysteine residues that form the active-site disulfide to yield a [Fe(4)S(4)](3+) cluster with two cysteinate ligands at a unique Fe site. The most intriguing result is that two-electron-reduced FTR in which the disulfide is reduced to a dithiol contains an unprecedented electron-rich [Fe(4)S(4)](2+) cluster comprising both valence-delocalized and valence-localized Fe(2+)Fe(3+) pairs. These results provide molecular level insights into the catalytic mechanism of FTR, and two viable mechanisms are proposed.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
0002-7863
pubmed:author
pubmed:issnType
Print
pubmed:day
6
pubmed:volume
127
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
9612-24
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
2005
pubmed:articleTitle
Spectroscopic characterization of site-specific [Fe(4)S(4)] cluster chemistry in ferredoxin:thioredoxin reductase: implications for the catalytic mechanism.
pubmed:affiliation
Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602, USA.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't, Research Support, N.I.H., Extramural