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Cysteine Substitution and Labeling Provide Insight into Channelrhodopsin-2 Ion Conductance
Ryan Richards1, Robert E Dempski1
1Department of Chemistry and Biochemistry, Worcester Polytechnic Institute , Worcester, Massachusetts 01609, United States.
Abstract:
Channelrhodopsin-2 is a light-activated cation channel. However, the mechanism of ion conductance is unresolved. Here, we performed cysteine scanning mutagenesis on transmembrane domain 7 followed by labeling with a methanethiosulfonate compound. Analysis of our results shows that residues that line the putative pore and interface with adjacent transmembrane domains 1 and 3, as proposed by our channelrhodopsin-2 homology model, affect ion conductance, decay kinetics, and/or off kinetics. Combined, these results suggest that negative charges at the extracellular side of transmembrane domain 7 funnel cations into the pore.
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