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Full-Text Articles in Biochemistry, Biophysics, and Structural Biology
Transmembrane Domain Three Contributes To The Ion Conductance Pathway Of Channelrhodopsin-2, Robert Dempski, Olga Gaiko
Transmembrane Domain Three Contributes To The Ion Conductance Pathway Of Channelrhodopsin-2, Robert Dempski, Olga Gaiko
Robert E. Dempski
Channelrhodopsin-2 (ChR2) is a light-activated nonselective cation channel that is found in the eyespot of the unicellular green alga Chlamydomonas reinhardtii. Despite the wide employment of this protein to control the membrane potential of excitable membranes, the molecular determinants that define the unique ion conductance properties of this protein are not well understood. To elucidate the cation permeability pathway of ion conductance, we performed cysteine scanning mutagenesis of transmembrane domain three followed by labeling with methanethiosulfonate derivatives. An analysis of our experimental results as modeled onto the crystal structure of the C1C2 chimera demonstrate that the ion permeation pathway includes …
Transmembrane Serine Mutations Reduce The Minimum Pore Diameter Of Channelrhodopsin-2, Robert Dempski, Ryan Richards
Transmembrane Serine Mutations Reduce The Minimum Pore Diameter Of Channelrhodopsin-2, Robert Dempski, Ryan Richards
Robert E. Dempski
Channelrhodopsin-2 (ChR2) is a microbial-type rhodopsin that, together with channelrhodopsin-1, mediates phototactic behavior in the green algae Chlamydomonas reinhardtii. Like all other microbial-type rhodopsins, ChR2 has seven transmembrane domains with the chromophore all-trans retinal bound to a single lysine residue. However, unlike other microbial-type rhodopsins, ChR2 functions as a non-selective cation channel and not an ion pump. A sequence alignment of ChR2 with the proton pump bacteriorhodopsin (bR) reveals that ChR2 lacks specific motifs within the transmembrane domains that facilitate non-covalent interactions and contribute to protein stability.