Gating mechanisms of a natural anion channelrhodopsin

摘要: Anion channelrhodopsins (ACRs) are a class of light-gated channels recently identified in cryptophyte algae that provide unprecedented fast and powerful hyperpolarizing tools for optogenetics. Analysis photocurrents generated by Guillardia theta ACR 1 (GtACR1) its mutants response to laser flashes showed GtACR1 gating comprises two separate mechanisms with opposite dependencies on the membrane voltage pH involving different amino acid residues. The first mechanism, characterized slow opening closing channel, is regulated Glu-68. Neutralization this residue (the E68Q mutation) specifically suppressed but did not eliminate it completely at high pH. Our data indicate involvement another, yet-unidentified pH-sensitive group X. Introducing positive charge Glu-68 site E68R inverted channel so was open dark closed light, without altering ion selectivity. second substantially affected mutation, controlled Cys-102. C102A mutation reduced rate mechanism ∼100-fold, whereas had only twofold effect first. results show anion conductance ACRs has fundamentally structural basis than relatively well studied cation (CCRs), attributable simply modification CCR selectivity filter.