Referenced in: none

Automatically associated channels: Slo1

Title: Kinetics of proton release and uptake by channelrhodopsin-2.

Authors: Melanie Nack, Ionela Radu, Bernd-Joachim Schultz, Tom Resler, Ramona Schlesinger, Ana-Nicoleta Bondar, Coral del Val, Stefania Abbruzzetti, Cristiano Viappiani, Christian Bamann, Ernst Bamberg, Joachim Heberle

Journal, date & volume: FEBS Lett., 2012 May 7 , 586, 1344-8

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/22504075

Abstract
Electrophysiological experiments showed that the light-activated cation channel channelrhodopsin-2 (ChR2) pumps protons in the absence of a membrane potential. We determined here the kinetics of transient pH change using a water-soluble pH-indicator. It is shown that ChR2 released protons prior to uptake with a stoichiometry of 0.3 protons per ChR2. Comparison to the photocycle kinetics revealed that proton release and uptake match rise and decay of the P(3)(520) intermediate. As the P(3)(520) state also represents the conductive state of cation channeling, the concurrence of proton pumping and channel gating implies an intimate mechanistic link of the two functional modes. Studies on the E123T and S245E mutants show that these residues are not critically involved in proton translocation.