Current address: Naoki Kamo, College of Pharmaceutical Science, Matsuyama University, Matsuyama 790 8578, Japan.
Photoreaction Cycle of Phoborhodopsin (Sensory Rhodopsin II) from Halobacterium salinarum Expressed in Escherichia coli
Article first published online: 22 JAN 2010
© 2010 The Authors. Journal Compilation. The American Society of Photobiology
Photochemistry and Photobiology
Volume 86, Issue 3, pages 571–579, May/June 2010
How to Cite
Dai, G., Ohno, Y., Ikeda, Y., Tamogami, J., Kikukawa, T., Kamo, N. and Iwasa, T. (2010), Photoreaction Cycle of Phoborhodopsin (Sensory Rhodopsin II) from Halobacterium salinarum Expressed in Escherichia coli. Photochemistry and Photobiology, 86: 571–579. doi: 10.1111/j.1751-1097.2009.00687.x
- Issue published online: 3 MAY 2010
- Article first published online: 22 JAN 2010
- Received 7 August 2009, accepted 10 November 2009
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, spR; also HsSRII) in Escherichia coli and purification method has been developed (Mironova et al.  FEBS Lett., 579, 3147–3151), which enables detailed studies on the photochemical properties of spR. In the present work, the photoreaction cycle of E. coli-expressed spR 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 spR at 20°C, formation of a new photoproduct P370 was observed and it decayed to the original spR in the dark with a decay half time of 190 min. Based on these results the similarities and dissimilarities between spR and ppR are discussed.