This paper is part of the Proceedings of the 13th International Conference on Retinal Proteins, Barcelona, Spain, 15–19 June 2008.
Functional Expression of the Signaling Complex Sensory Rhodopsin II/Transducer II from Halobacterium salinarum in Escherichia coli†
Article first published online: 19 NOV 2008
© 2008 The Authors. Journal Compilation. The American Society of Photobiology
Photochemistry and Photobiology
Volume 85, Issue 2, pages 521–528, March/April 2009
How to Cite
Kim, Y.-J., Chizhov, I. and Engelhard, M. (2009), Functional Expression of the Signaling Complex Sensory Rhodopsin II/Transducer II from Halobacterium salinarum in Escherichia coli. Photochemistry and Photobiology, 85: 521–528. doi: 10.1111/j.1751-1097.2008.00470.x
- Issue published online: 25 FEB 2009
- Article first published online: 19 NOV 2008
- Received 15 August 2008, accepted 3 September 2008
Sensory rhodopsin II, a photoreceptor from Halobacterium salinarum (HsSRII), in complex with its cognate transducer protein (HsHtrII) triggers the photophobic response via a cytoplasmic two-component signaling cascade. HsHtrII possess in addition to the HsSRII binding and the cytoplasmic domains an extracellular serine-receptor domain. Here we describe the properties of HsSRII and HsHtrII and those of various shortened transducer analogs, heterologously expressed in Escherichia coli. HsSRII displays the photocycle typical of archaeal photosensors with prolonged kinetics. Using an isothermal titration calorimetric analysis for this complex a dissociation constant of 1.1 μm was obtained similar to that of the corresponding transducer/receptor pair from Natronobacterium pharaonis. A shortened transducer lacking the extracellular and cytoplasmic domain is also sufficient to bind the receptor with a slightly lower affinity. The dissociation constant of serine binding to the extracellular domain was determined to be about 5 μm. This result is in line with the proposal that the extracellular domain indeed is a serine receptor.