Linked Life Data

17623666

Source:http://linkedlifedata.com/resource/pubmed/id/17623666

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
38
pubmed:dateCreated
2007-9-14
pubmed:abstractText
Cytochromes cd(1) are dimeric bacterial nitrite reductases, which contain two hemes per monomer. On reduction of both hemes, the distal ligand of heme d(1) dissociates, creating a vacant coordination site accessible to substrate. Heme c, which transfers electrons from donor proteins into the active site, has histidine/methionine ligands except in the oxidized enzyme from Paracoccus pantotrophus where both ligands are histidine. During reduction of this enzyme, Tyr(25) dissociates from the distal side of heme d(1), and one heme c ligand is replaced by methionine. Activity is associated with histidine/methionine coordination at heme c, and it is believed that P. pantotrophus cytochrome cd(1) is unreactive toward substrate without reductive activation. However, we report here that the oxidized enzyme will react with nitrite to yield a novel species in which heme d(1) is EPR-silent. Magnetic circular dichroism studies indicate that heme d(1) is low-spin Fe(III) but EPR-silent as a result of spin coupling to a radical species formed during the reaction with nitrite. This reaction drives the switch to histidine/methionine ligation at Fe(III) heme c. Thus the enzyme is activated by exposure to its physiological substrate without the necessity of passing through the reduced state. This reactivity toward nitrite is also observed for oxidized cytochrome cd(1) from Pseudomonas stutzeri suggesting a more general involvement of the EPR-silent Fe(III) heme d(1) species in nitrite reduction.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Sep
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
21
pubmed:volume
282
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
28207-15
pubmed:meshHeading
pubmed:year
2007
pubmed:articleTitle
Activation of the cytochrome cd1 nitrite reductase from Paracoccus pantotrophus. Reaction of oxidized enzyme with substrate drives a ligand switch at heme c.
pubmed:affiliation
Centre for Metalloprotein Spectroscopy and Biology, School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich NR4 7TJ, United Kingdom.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't