Patent ID: 8263412

Claim:
A method for screening the effects of a test compound on ion channel activity in a cell comprising the steps of, i) providing a cell comprising an ion channel of interest and an engineered green fluorescent protein comprising an amino acid sequence at least 85% identical to the amino acid sequence of the Aequorea green fluorescent protein set forth in SEQ ID NO:2 and which differs from SEQ ID NO:2 by (1) at least one first substitution at position T203, wherein the substituting amino acid is selected from the group consisting of H, Y, W and F, (2) at least one second substitution at position H148, wherein the substituting amino acid is selected from the group consisting of R, G, Q, A, N, and K, and (3) at least one third amino acid substitution at position V150, wherein the substituting amino acid is selected from the group consisting of A, C, M, G, L, Q, S, T and N; and ii) contacting said cell with the test compound, iii) measuring fluorescence from said engineered green fluorescent protein, and iv) comparing the fluorescence of said engineered green fluorescent protein in said cell to the fluorescence of a control engineered green fluorescent protein introduced into a control cell wherein the control cell is not contacted with the test compound.