Linked Life Data

14551217

Source:http://linkedlifedata.com/resource/pubmed/id/14551217

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
52
pubmed:dateCreated
2003-12-22
pubmed:abstractText
ATPase activity associated with P-glycoprotein (Pgp) is characterized by three drug-dependent phases: basal (no drug), drug-activated, and drug-inhibited. To understand the communication between drug-binding sites and ATP hydrolytic sites, we performed steady-state thermodynamic analyses of ATP hydrolysis in the presence and absence of transport substrates. We used purified human Pgp (ABCB1, MDR1) expressed in Saccharomyces cerevisiae (Figler, R. A., Omote, H., Nakamoto, R. K., and Al-Shawi, M. K. (2000) Arch. Biochem. Biophys. 376, 34-46) as well as Chinese hamster Pgp (PGP1). Between 23 and 35 degrees C, we obtained linear Arrhenius relationships for the turnover rate of hydrolysis of saturating MgATP in the presence of saturating drug concentrations (kcat), from which we calculated the intrinsic enthalpic, entropic, and free energy terms for the rate-limiting transition states. Linearity of the Arrhenius plots indicated that the same rate-limiting step was being measured over the temperature range employed. Using linear free energy analysis, two distinct transition states were found: one associated with uncoupled basal activity and the other with coupled drug transport activity. We concluded that basal ATPase activity associated with Pgp is not a consequence of transport of an endogenous lipid or other endogenous substrates. Rather, it is an intrinsic mechanistic property of the enzyme. We also found that rapidly transported substrates bound tighter to the transition state and required fewer conformational alterations by the enzyme to achieve the coupling transition state. The overall rate-limiting step of Pgp during transport is a carrier reorientation step. Furthermore, Pgp is optimized to transport drugs out of cells at high rates at the expense of coupling efficiency. The drug inhibition phase was associated with low affinity drug-binding sites. These results are consistent with an expanded version of the alternating catalytic site drug transport model (Senior, A. E., Al-Shawi, M. K., and Urbatsch, I. L. (1995) FEBS Lett. 377, 285-289). A new kinetic model of drug transport is presented.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
26
pubmed:volume
278
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
52629-40
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed-meshheading:14551217-Adenosine Triphosphatases, pubmed-meshheading:14551217-Adenosine Triphosphate, pubmed-meshheading:14551217-Animals, pubmed-meshheading:14551217-Binding Sites, pubmed-meshheading:14551217-CHO Cells, pubmed-meshheading:14551217-Catalysis, pubmed-meshheading:14551217-Colchicine, pubmed-meshheading:14551217-Cricetinae, pubmed-meshheading:14551217-Dose-Response Relationship, Drug, pubmed-meshheading:14551217-Entropy, pubmed-meshheading:14551217-Humans, pubmed-meshheading:14551217-Hydrolysis, pubmed-meshheading:14551217-Kinetics, pubmed-meshheading:14551217-Lipids, pubmed-meshheading:14551217-Models, Biological, pubmed-meshheading:14551217-P-Glycoprotein, pubmed-meshheading:14551217-Plant Oils, pubmed-meshheading:14551217-Protein Conformation, pubmed-meshheading:14551217-Saccharomyces cerevisiae, pubmed-meshheading:14551217-Temperature, pubmed-meshheading:14551217-Thermodynamics, pubmed-meshheading:14551217-Time Factors, pubmed-meshheading:14551217-Verapamil
pubmed:year
2003
pubmed:articleTitle
Transition state analysis of the coupling of drug transport to ATP hydrolysis by P-glycoprotein.
pubmed:affiliation
Department of Molecular Physiology and Biological Physics, University of Virginia Health System, Charlottesville, Virginia 22908-0736, USA. ma9a@virginia.edu
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.