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Photoreaction Cycle of Phoborhodopsin (Sensory Rhodopsin II) from Halobacterium salinarum Expressed in Escherichia coli
Author(s) -
Dai Gang,
Ohno Yoshikazu,
Ikeda Yoichi,
Tamogami Jun,
Kikukawa Takashi,
Kamo Naoki,
Iwasa Tatsuo
Publication year - 2010
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.2009.00687.x
Subject(s) - halobacterium salinarum , flash photolysis , bacteriorhodopsin , rhodopsin , phototaxis , escherichia coli , photochemistry , chemistry , pigment , halobacteriaceae , photodissociation , halobacterium , biology , biophysics , biochemistry , kinetics , organic chemistry , retinal , botany , physics , gene , reaction rate constant , quantum mechanics , membrane
Phoborhodopsin (pR; also called sensory rhodopsin II, SRII) is a photoreceptor of negative phototaxis of halobacteria. The studies of photochemical properties of this pigment are not many because the amount of the pigment is small and the stability is low. Recently an expression system of phoborhodopsin from Halobacterium salinarum (called salinarum phoborhodopsin, s pR; also Hs SRII) in Escherichia coli and purification method has been developed (Mironova et al. [2005] FEBS Lett. , 579, 3147–3151), which enables detailed studies on the photochemical properties of s pR. In the present work, the photoreaction cycle of E. coli ‐expressed s pR was studied by low‐temperature spectroscopy and flash photolysis. Formations of K‐, M‐, O‐like intermediates and P480 were reconfirmed as reported previously. New findings are as follows. (1) The K‐like intermediate (P500) was a mixture of two photoproducts. (2) Formation of L‐like intermediate (P482) was observed by low‐temperature spectroscopy and flash photolysis at room temperature. (3) On long irradiation of s pR at 20°C, formation of a new photoproduct P370 was observed and it decayed to the original s pR in the dark with a decay half time of 190 min. Based on these results the similarities and dissimilarities between s pR and p pR are discussed.