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Synergistic substrate binding determines the stoichiometry of transport of a prokaryotic H(+)/Cl(-) exchanger

Picollo, Alessandra and Xu, Yanyan and Johner, Niklaus and Bernèche, Simon and Accardi, Alessio. (2012) Synergistic substrate binding determines the stoichiometry of transport of a prokaryotic H(+)/Cl(-) exchanger. Nature structural & molecular biology, Vol. 19, no. 5. pp. 525-531.

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Official URL: http://edoc.unibas.ch/dok/A6002723

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Abstract

Active exchangers dissipate the gradient of one substrate to accumulate nutrients, export xenobiotics and maintain cellular homeostasis. Mechanistic studies have suggested that two fundamental properties are shared by all exchangers: substrate binding is antagonistic, and coupling is maintained by preventing shuttling of the empty transporter. The CLC H(+)/Cl(-) exchangers control the homeostasis of cellular compartments in most living organisms, but their transport mechanism remains unclear. We show that substrate binding to CLC-ec1 is synergistic rather than antagonistic: chloride binding induces protonation of a crucial glutamate. The simultaneous binding of H(+) and Cl(-) gives rise to a fully loaded state that is incompatible with conventional transport mechanisms. Mutations in the Cl(-) transport pathway identically alter the stoichiometries of H(+)/Cl(-) exchange and binding. We propose that the thermodynamics of synergistic substrate binding, rather than the kinetics of conformational changes and ion binding, determine the stoichiometry of transport.
Faculties and Departments:05 Faculty of Science > Departement Biozentrum > Former Organization Units Biozentrum > Computational Biophysics (Bernèche)
UniBasel Contributors:Bernèche, Simon
Item Type:Article, refereed
Article Subtype:Research Article
Bibsysno:Link to catalogue
Publisher:Nature Publ. Group
ISSN:1545-9993
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:29 Jan 2016 07:45
Deposited On:11 Oct 2012 15:19

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