Functional expression of His-tagged sensory rhodopsin I in Escherichia coli

Sensory rhodopsin I (SRI) from Halobacterium salinarum was functionally exp ressed in Escherichia coli and subsequently purified to homogeneity using a C-terminal His-tag anchor. Yields of 3-4 mg SRI/I cell culture can be obta ined, The absorption and photocycle properties of SRI were similar if not i ndistinguishable from those of the homologously expressed SRI. A global fit analysis of the photocycle data and the calculation of the spectra of stat es provided strong evidence for the existence of an N-like intermediate. (C ) 2000 Federation of European Biochemical Societies.