10.1016/j.bpj.2009.10.052

Two Open States with Progressive Proton Selectivities in the Branched Channelrhodopsin-2 Photocycle

Abstract

AbstractChannelrhodopsins are light-gated ion channels that mediate vision in phototactic green algae like Chlamydomonas. In neurosciences, channelrhodopsins are widely used to light-trigger action potentials in transfected cells. All known channelrhodopsins preferentially conduct H+. Previous studies have indicated the existence of an early and a late conducting state within the channelrhodopsin photocycle. Here, we show that for channelrhodopsin-2 expressed in Xenopus oocytes and HEK cells, the two open states have different ion selectivities that cause changes in the channelrhodopsin-2 reversal voltage during a light pulse. An enzyme kinetic algorithm was applied to convert the reversal voltages in various ionic conditions to conductance ratios for H+ and divalent cations (Ca2+ and/or Mg2+), as compared to monovalent cations (Na+ and/or K+). Compared to monovalent cation conductance, the H+ conductance, α, is ∼3 × 106 and the divalent cation conductance, β, is ∼0.01 in the early conducting state. In the stationary mixture of the early and late states, α is larger and β smaller, both by a factor of ∼2. The results suggest that the ionic basis of light perception in Chlamydomonas is relatively nonspecific in the beginning of a light pulse but becomes more selective for protons during longer light exposures

Similar works

Full text

thumbnail-image

Elsevier - Publisher Connector

Provided original full text link
Last time updated on 6/5/2019

This paper was published in Elsevier - Publisher Connector .

Having an issue?

Is data on this page outdated, violates copyrights or anything else? Report the problem now and we will take corresponding actions after reviewing your request.