Linked Life Data

16925440

Source:http://linkedlifedata.com/resource/pubmed/id/16925440

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
34
pubmed:dateCreated
2006-8-23
pubmed:abstractText
Nitrile hydratase (NHase) is one of a growing number of enzymes shown to contain post-translationally modified cysteine sulfenic acids (Cys-SOH). Cysteine sulfenic acids have been shown to play diverse roles in cellular processes, including transcriptional regulation, signal transduction, and the regulation of oxygen metabolism and oxidative stress responses. The function of the cysteine sulfenic acid coordinated to the iron active site of NHase is unknown. Herein we report the first example of a sulfenate-ligated iron complex, [Fe(III)(ADIT)(ADIT-O)](+) (5), and compare its electronic and magnetic properties with those of structurally related complexes in which the sulfur oxidation state and protonation state have been systematically altered. Oxygen atom addition was found to decrease the unmodified thiolate Fe-S bond length and blue-shift the ligand-to-metal charge-transfer band (without loss of intensity). S K-edge X-ray absorption spectroscopy and density functional theory calculations show that, although the modified RS-O(-) fragment is incapable of forming a pi bond with the Fe(III) center, the unmodified thiolate compensates for this loss of pi bonding by increasing its covalent bond strength. The redox potential shifts only slightly (75 mV), and the magnetic properties are not affected (the S = (1)/(2) spin state is maintained). The coordinated sulfenate S-O bond is activated and fairly polarized (S(+)-O(-)). Addition of strong acids at low temperatures results in the reversible protonation of sulfenate-ligated 5. An X-ray structure demonstrates that Zn(2+) binds to the sulfenate oxygen to afford [Fe(III)(ADIT)(ADIT-O-ZnCl(3))] (6). The coordination of ZnCl(3)(-) to the RS-O(-) unit causes the covalent overlap with the unmodified thiolate to increase further. A possible catalytic role for the unmodified NHase thiolate, involving its ability to "tune" the electronics in response to protonation of the sulfenate (RS-O(-)) oxygen and/or substrate binding, is discussed.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Aug
pubmed:issn
0002-7863
pubmed:author
pubmed:issnType
Print
pubmed:day
30
pubmed:volume
128
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
11211-21
pubmed:dateRevised
2007-12-3
pubmed:meshHeading
pubmed:year
2006
pubmed:articleTitle
How does single oxygen atom addition affect the properties of an Fe-nitrile hydratase analogue? The compensatory role of the unmodified thiolate.
pubmed:affiliation
Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, Non-P.H.S., Research Support, N.I.H., Extramural