Channelrhodopsin variants and uses thereof

A method of altering ion conductivity of a membrane, the method comprising,

• a) expressing in a host membrane a CsChrimson light-activated ion channel polypeptide comprising (a) the amino acid sequence set forth as SEQ ID NO:
• 1 or (b) the amino acid sequence of SEQ ID NO:
• 1 with one, two, three, or more amino acid sequence modifications within the sequence, and having at least 97% identity to amino acids 1-79 of SEQ ID NO:
• 1 and a seven-transmembrane-domain region having at least 97% identity to amino acids 80-315 of SEQ ID NO:
• 1, and wherein the CsChrimson light-activated ion channel polypeptide is capable of being activated with light, and the activation alters ion conductivity of the CsChrimson light-activated ion channel polypeptide;
• and
• b) contacting the CsChrimson light-activated ion channel polypeptide with a light under suitable conditions to activate the light-activated ion channel and alter the ion conductivity of the membrane.

A method of assessing the effect of a candidate compound on ion conductivity of a membrane, the method comprising,

• a) contacting a test membrane comprising a light-activated ion channel polypeptide comprising (a) the amino acid sequence set forth as SEQ ID NO:
• 1 or (b) the amino acid sequence of SEQ ID NO:
• 1 with one, two, three, or more amino acid sequence modifications within the sequence, and having at least 97% identity to amino acids 1-79 of SEQ ID NO:
• 1 and a seven-transmembrane-domain region having at least 97% identity to amino acids 80-315 of SEQ ID NO:
• 1, and wherein the CsChrimson light-activated ion channel polypeptide is capable of being activated with light, and the activation alters ion conductivity of the CsChrimson light-activated ion channel polypeptide, with light under conditions suitable for altering ion conductivity of the test membrane;
• b) contacting the test membrane with a candidate compound;
• and
• c) identifying the presence or absence of a change in ion conductivity of the test membrane contacted with the light and the candidate compound compared to ion conductivity of with “a control test membrane comprising the light-activated ion channel polypeptide contacted with light, and not contacted with the candidate compound;
• wherein a change in the ion conductivity of the test membrane compared to the control indicates an effect of the candidate compound on the ion conductivity of the test membrane.