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Strict coupling between CFTR's catalytic cycle and gating of its Cl- ion pore revealed by distributions of open channel burst durations

Csanady, L; Vergani, P; Gadsby, DC; (2010) Strict coupling between CFTR's catalytic cycle and gating of its Cl- ion pore revealed by distributions of open channel burst durations. Proceedings of the National Academy of Sciences USA , 107 (3) 1241 - 1246. 10.1073/pnas.0911061107. Green open access

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Abstract

CFTR, the ABC protein defective in cystic fibrosis, functions as an anion channel. Once phosphorylated by protein kinase A, a CFTR channel is opened and closed by events at its two cytosolic nucleotide binding domains (NBDs). Formation of a head-to-tail NBD1/NBD2 heterodimer, by ATP binding in two interfacial composite sites between conserved Walker A and B motifs of one NBD and the ABC-specific signature sequence of the other, has been proposed to trigger channel opening. ATP hydrolysis at the only catalytically competent interfacial site is suggested to then destabilize the NBD dimer and prompt channel closure. But this gating mechanism, and how tightly CFTR channel opening and closing are coupled to its catalytic cycle, remains controversial. Here we determine the distributions of open burst durations of individual CFTR channels, and use maximum likelihood to evaluate fits to equilibrium and nonequilibrium mechanisms and estimate the rate constants that govern channel closure. We examine partially and fully phosphorylated wild-type CFTR channels, and two mutant CFTR channels, each bearing a deleterious mutation in one or other composite ATP binding site. We show that the wild-type CFTR channel gating cycle is essentially irreversible and tightly coupled to the ATPase cycle, and that this coupling is completely destroyed by the NBD2Walker B mutation D1370N but only partially disrupted by the NBD1 Walker A mutation K464A.

Type: Article
Title: Strict coupling between CFTR's catalytic cycle and gating of its Cl- ion pore revealed by distributions of open channel burst durations
Open access status: An open access version is available from UCL Discovery
DOI: 10.1073/pnas.0911061107
Publisher version: http://dx.doi.org/10.1073/pnas.0911061107
Language: English
Additional information: © 2010 National Academy of Sciences.
Keywords: ATPase cycle, maximum likelihood, nonequilibrium, phosphorylation, Walker motifs, TRANSMEMBRANE CONDUCTANCE REGULATOR, NUCLEOTIDE-BINDING DOMAIN, ATP HYDROLYSIS CYCLE, ABC TRANSPORTER, P-GLYCOPROTEIN, CHLORIDE CHANNELS, KINETIC-ANALYSIS, CONFORMATION, MUTATIONS, MECHANISM
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences > Neuro, Physiology and Pharmacology
URI: https://discovery.ucl.ac.uk/id/eprint/91743
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