Linked Life Data

9548936

Source:http://linkedlifedata.com/resource/pubmed/id/9548936

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
16
pubmed:dateCreated
1998-5-14
pubmed:abstractText
Ribonucleoside triphosphate reductase (RTPR) from Lactobacillus leichmannii utilizes adenosylcobalamin and catalyzes the conversion of nucleoside triphosphates to deoxynucleoside triphosphates. One equivalent of 2',2'-difluoro-2'-deoxycytidine 5'-triphosphate, F2dCTP, rapidly inactivates RTPR. Analysis of the reaction products reveals that inactivation is accompanied by release of two fluoride ions and 0.84 equiv of 5'-deoxyadenosine and attachment of 1 equiv of corrin covalently to an active-site cysteine residue of RTPR. No cytosine release was detected. Proteolysis of corrin-labeled RTPR with endoproteinase Glu-C and peptide mapping at pH 5.8 revealed that C419 was predominantly modified. The kinetics of the inactivation have been examined by stopped-flow (SF) UV-vis spectroscopy and rapid freeze quench (RFQ) electron paramagnetic resonance (EPR) spectroscopy. Monitoring DeltaA525 nm shows that cob(II)alamin is formed with an apparent kobs of 50 s-1, only 2. 5-fold slower than a similar experiment carried out with cytidine 5'-triphosphate (CTP). The same reaction mixture was thus quenched at times from 22 ms to 30 s and examined by EPR spectroscopy. At early time points the EPR spectrum resembled a thiyl radical exchange coupled to cob(II)alamin. From 22 to 255 ms the total spin concentration remained unchanged at 1.4 spins/RTPR, twice that predicted by the amount of cob(II)alamin determined by SF. However, with time the signal attributed to the thiyl radical-cob(II)alamin disappears and new signal(s) with broad feature(s) at g = 2.33 and a sharp feature at g = 2.00 appeared, suggesting formation of cob(II)alamin and a nucleotide-based radical with only dipolar interactions. These studies have been interpreted to support the proposal that an RTPR-based thiyl radical can give rise to a nucleotide-based radical.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
http://linkedlifedata.com/resource/pubmed/chemical/5'-deoxyadenosine, http://linkedlifedata.com/resource/pubmed/chemical/Cytosine, http://linkedlifedata.com/resource/pubmed/chemical/Deoxyadenosines, http://linkedlifedata.com/resource/pubmed/chemical/Deoxycytidine, http://linkedlifedata.com/resource/pubmed/chemical/Enzyme Inhibitors, http://linkedlifedata.com/resource/pubmed/chemical/Fluorides, http://linkedlifedata.com/resource/pubmed/chemical/Free Radicals, http://linkedlifedata.com/resource/pubmed/chemical/Peptides, http://linkedlifedata.com/resource/pubmed/chemical/Ribonucleotide Reductases, http://linkedlifedata.com/resource/pubmed/chemical/Sulfhydryl Compounds, http://linkedlifedata.com/resource/pubmed/chemical/Vitamin B 12, http://linkedlifedata.com/resource/pubmed/chemical/gemcitabine
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
21
pubmed:volume
37
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
5528-35
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1998
pubmed:articleTitle
Gemcitabine 5'-triphosphate is a stoichiometric mechanism-based inhibitor of Lactobacillus leichmannii ribonucleoside triphosphate reductase: evidence for thiyl radical-mediated nucleotide radical formation.
pubmed:affiliation
Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't