Linked Life Data

17553785

Source:http://linkedlifedata.com/resource/pubmed/id/17553785

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
34
pubmed:dateCreated
2007-8-20
pubmed:abstractText
We demonstrate that photoexcitation of NAD(P)H reduces heme iron of Mycobacterium tuberculosis P450s CYP121 and CYP51B1 on the microsecond time scale. Rates of formation for the ferrous-carbonmonoxy (Fe(II)-CO) complex were determined across a range of coenzyme/CO concentrations. CYP121 reaction transients were biphasic. A hyperbolic dependence on CO concentration was observed, consistent with the presence of a CO binding site in ferric CYP121. CYP51B1 absorption transients for Fe(II)-CO complex formation were monophasic. The reaction rate was second order with respect to [CO], suggesting the absence of a CO-binding site in ferric CYP51B1. In the absence of CO, heme iron reduction by photoexcited NAD(P)H is fast ( approximately 10,000-11,000 s(-1)) with both P450s. For CYP121, transients revealed initial production of the thiolate-coordinated (P450) complex (absorbance maximum at 448 nm), followed by a slower phase reporting partial conversion to the thiol-coordinated P420 species (at 420 nm). The slow phase amplitude increased at lower pH values, consistent with heme cysteinate protonation underlying the transition. Thus, CO binding occurs to the thiolate-coordinated ferrous form prior to cysteinate protonation. For CYP51B1, slow conversions of both the ferrous/Fe(II)-CO forms to species with spectral maxima at 423/421.5 nm occurred following photoexcitation in the absence/presence of CO. This reflected conversion from ferrous thiolate- to thiol-coordinated forms in both cases, indicating instability of the thiolate-coordinated ferrous CYP51B1. CYP121 Fe(II)-CO complex pH titrations revealed reversible spectral transitions between P450 and P420 forms. Our data provide strong evidence for P420 formation linked to reversible heme thiolate protonation, and demonstrate key differences in heme chemistry and CO binding for CYP121 and CYP51B1.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Aug
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
24
pubmed:volume
282
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
24816-24
pubmed:meshHeading
pubmed:year
2007
pubmed:articleTitle
Rapid P450 heme iron reduction by laser photoexcitation of Mycobacterium tuberculosis CYP121 and CYP51B1. Analysis of CO complexation reactions and reversibility of the P450/P420 equilibrium.
pubmed:affiliation
Manchester Interdisciplinary Biocentre, Faculty of Life Sciences, University of Manchester, 131 Princess Street, Manchester M1 7DN.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't