Patent ID: 8828658

Claim:
A method of spatially and/or temporally regulating an interaction between a first protein sequence and a second protein sequence within a cell by light, comprising: a) providing in the cell a first protein construct which comprises the first protein sequence and a phytochrome domain (PHD), wherein the phytochrome domain: (i) can reversibly convert from a red-light absorbing conformer (Pr state) to a far-red light-absorbing conformer (Pfr state) upon exposure to red light, and (ii) can reversibly convert from the Pfr state to the Pr state upon exposure to infra-red light; b) providing in the cell a second protein construct which comprises the second protein sequence and a phytochrome domain-interacting peptide (PIP) that can bind selectively to the Pfr state, but not to the Pr state, of the phytochrome domain; and c) regulating the interaction between the first protein construct and the second protein construct by regulating cell exposure to red light and/or infra-red light, and d) detecting a change in the interaction between the first protein construct and the second protein construct within the cell, wherein: (i) the PHD comprises a partial fragment of PhyB from Arabidopsis thaliana , and the PIP comprises the APB domain of PIF6; or (ii) the first protein construct or second protein construct can be optically detected, and the change in interaction is detected by optically detecting its spatial distribution; or (iii) the change in interaction can be detected within one minute of exposure to regulatory red or infra-red light; or (iv) a portion of the cell is exposed to regulatory red or infra-red light and the change in interaction is spatially localized within a few microns of the exposed portion.