An interfacial sodium is an essential structural feature of Fluc family fluoride channels

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 mainchain carbonyl oxygens from the mid-membrane breaks in two corresponding transmembran...

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Bibliographic Details
Published in:Journal of molecular biology 2020-01, Vol.432 (4), p.1098-1108
Main Authors: McIlwain, Benjamin C., Martin, Kamirah, Hayter, Elizabeth A., Stockbridge, Randy B.
Format: Article
Language:English
Online Access:Get full text
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Summary: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 mainchain carbonyl oxygens from the mid-membrane 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.
ISSN:0022-2836
1089-8638
DOI:10.1016/j.jmb.2020.01.007