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Updated: May 7, 2026

Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels
Published on: July 4, 2016
Structural differences between the closed and open states of channelrhodopsin-2 as observed by EPR spectroscopy
Nils Krause1, Christopher Engelhard, Joachim Heberle
1Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin, Germany.
Abstract:
Channelrhodopsin is a cation channel with the unique property of being activated by light. To address structural changes of the open state of the channel, two variants, which contain either 1 or 2 wild-type cysteines, were derivatised with nitroxide spin label and subjected to electron paramagnetic resonance spectroscopy. Both variants contained the C128T mutation to trap the long-lived P3(520) state by illumination. Comparison of spin-spin distances in the dark state and after illumination reflect conformational changes in the conductive P3(520) state involving helices B and F. Spin distance measurements reveal that channelrhodopsin forms a dimer even in the absence of intermolecular N-terminal cysteines.
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