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Biophys J. 2016 Jun 7;110(11):2302-2304. doi: 10.1016/j.bpj.2016.05.001. Epub 2016 May 24.

Structurally Distinct Cation Channelrhodopsins from Cryptophyte Algae.

Author information

1
Center for Membrane Biology and Department of Biochemistry and Molecular Biology, University of Texas Health Science Center at Houston, McGovern Medical School, Houston, Texas.
2
Center for Membrane Biology and Department of Biochemistry and Molecular Biology, University of Texas Health Science Center at Houston, McGovern Medical School, Houston, Texas. Electronic address: john.l.spudich@uth.tmc.edu.

Abstract

Microbial rhodopsins are remarkable for the diversity of their functional mechanisms based on the same protein scaffold. A class of rhodopsins from cryptophyte algae show close sequence homology with haloarchaeal rhodopsin proton pumps rather than with previously known channelrhodopsins from chlorophyte (green) algae. In particular, both aspartate residues that occupy the positions of the chromophore Schiff base proton acceptor and donor, a hallmark of rhodopsin proton pumps, are conserved in these cryptophyte proteins. We expressed the corresponding polynucleotides in human embryonic kidney (HEK293) cells and studied electrogenic properties of the encoded proteins with whole-cell patch-clamp recording. Despite their lack of residues characteristic of the chlorophyte cation channels, these proteins are cation-conducting channelrhodopsins that carry out light-gated passive transport of Na(+) and H(+). These findings show that channel function in rhodopsins has evolved via multiple routes.

PMID:
27233115
PMCID:
PMC4906376
DOI:
10.1016/j.bpj.2016.05.001
[Indexed for MEDLINE]
Free PMC Article

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