Mar 21, 2020

Conductance mechanisms of rapidly desensitizing cation channelrhodopsins from cryptophyte algae

BioRxiv : the Preprint Server for Biology
O. A. SineshchekovJohn L. Spudich


Channelrhodopsins guide algal phototaxis and are widely used as optogenetic probes for control of membrane potential with light. "Bacteriorhodopsin-like" cation channelrhodopsins (BCCRs) from cryptophytes differ in primary structure from other CCRs, lacking usual residues important for their cation conductance. Instead, BCCR sequences match more closely those of rhodopsin proton pumps, containing residues responsible for critical proton transfer reactions. We report 19 new BCCRs, which, together with the earlier 6 known members of this family, form three branches (subfamilies) of a phylogenetic tree. Here we show that the conductance mechanisms in two subfamilies differ with respect to involvement of the homolog of the proton donor in rhodopsin pumps. Two BCCRs from the genus Rhodomonas generate photocurrents that rapidly desensitize under continuous illumination. Using a combination of patch clamp electrophysiology, absorption and Raman spectroscopy, and flash photolysis, we found that the desensitization is due to rapid accumulation of a long-lived nonconducting intermediate of the photocycle with unusually blue-shifted absorption with a maximum at 330 nm. These observations reveal diversity within the BCCR family and contrib...Continue Reading

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Mentioned in this Paper

Genome-Wide Association Study
Hemifacial Microsomia
Pathogenic Organism
Morphologically Abnormal Structure (Morphologic Abnormality)
Genetic Pedigree
Whole Exome Sequencing

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