The branched photocycle of the slow-cycling channelrhodopsin-2 mutant C128T - PubMed (original) (raw)

. 2010 May 21;398(5):690-702.

doi: 10.1016/j.jmb.2010.03.031. Epub 2010 Mar 25.

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The branched photocycle of the slow-cycling channelrhodopsin-2 mutant C128T

Katja Stehfest et al. J Mol Biol. 2010.

Abstract

Channelrhodopsins (ChRs) of green algae such as Chlamydomonas are used as neuroscience tools to specifically depolarize cells with light. A crude model of the ChR2 photocycle has been recently established, but details of the photoreactions are widely unknown. Here, we present the photoreactions of a slow-cycling ChR2 mutant (step function rhodopsin), with C128 replaced by threonine and 200-fold extended lifetime of the conducting-state P520. At a late state of the photocycle, a fraction of the proteins branches off into an inactive species, P380, which accumulates during prolonged illumination. At neutral pH, P380 is converted into P353, a species with a characteristic fine-structured spectrum that is interpreted as retroretinyl chromophore. The described branching reactions should be considered, when ChR is used as a neuroscience tool, especially in the case of fluorescence imaging at high light intensities.

(c) 2010 Elsevier Ltd. All rights reserved.

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