An Interfacial Sodium Ion is an Essential Structural Feature of Fluc Family Fluoride Channels.

Autor: McIlwain BC; Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA., Martin K; Program in Biophysics, University of Michigan, Ann Arbor, MI 48109, USA., Hayter EA; Program in Biophysics, University of Michigan, Ann Arbor, MI 48109, USA., Stockbridge RB; Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA; Program in Biophysics, University of Michigan, Ann Arbor, MI 48109, USA. Electronic address: stockbr@umich.edu.
Jazyk: angličtina
Zdroj: Journal of molecular biology [J Mol Biol] 2020 Feb 14; Vol. 432 (4), pp. 1098-1108. Date of Electronic Publication: 2020 Jan 14.
DOI: 10.1016/j.jmb.2020.01.007
Abstrakt: Fluc family fluoride channels are assembled as primitive antiparallel homodimers. Crystallographic studies revealed a cation bound at the center of the protein, where it is coordinated at the dimer interface by main chain carbonyl oxygen atoms from the midmembrane breaks in two corresponding transmembrane helices. Here, we show that this cation is a stably bound sodium ion, and although it is not a transported substrate, its presence is required for the channel to adopt an open, fluoride-conducting conformation. The interfacial site is selective for sodium over other cations, except for Li + , which competes with Na + for binding, but does not support channel activity. The strictly structural role fulfilled by this sodium provides new context to understand the structures, mechanisms, and evolutionary origins of widespread Na + -coupled transporters.
(Copyright © 2020 Elsevier Ltd. All rights reserved.)
Databáze: MEDLINE
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