Characterization of a signaling complex composed of sensory rhodopsin I and its cognate transducer protein from the eubacterium Salinibacter ruber.
Sensory rhodopsin I (SRI) exists in the cell membranes of microorganisms such as the archaeon Halobacterium salinarum and is a photosensor responsible for positive and negative phototaxis. SRI forms a signaling complex with its cognate transducer protein, HtrI, in the membrane. That complex transmits light signals to the flagellar motor through changes in protein-protein interactions with the kinase CheA and the adaptor protein CheW, which controls the direction of the rotation of the flagellar motor. Recently, we cloned and characterized Salinibacter sensory rhodopsin I (SrSRI), which is the first SRI-like protein identified in eubacteria [Kitajima-Ihara, T., et al. (2008) J. Biol. Chem. 283, 23533-23541]. Here we cloned and expressed SrSRI with its full-length transducer protein, SrHtrI, as a fusion construct. We succeeded in producing the complex in Escherichia coli as a recombinant protein with high quality having all-trans-retinal as a chromophore for SRI, although the expression level was low (0.10 mg/L of culture). In addition, we report here the photochemical properties of the SrSRI-SrHtrI complex using time-resolved laser flash spectroscopy and other spectroscopic techniques and compare them to SrSRI without SrHtrI.
Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan. z47867a@cc.nagoya-u.ac.jp
Yuki
Y
Sudo
Akiko
A
Okada
Daisuke
D
Suzuki
Keiichi
K
Inoue
Hiroki
H
Irieda
Makoto
M
Sakai
Masaaki
M
Fujii
Yuji
Y
Furutani
Hideki
H
Kandori
Michio
M
Homma
D001665:Binding Sites; D019617:Halobacterium salinarum / Q000378:metabolism; D025602:Halorhodopsins / Q000737:chemistry; D055537:Light Signal Transduction; D008958:Models, Molecular; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D025604:Rhodopsins, Microbial / Q000737:chemistry* / Q000378:metabolism; D025603:Sensory Rhodopsins / Q000737:chemistry* / Q000378:metabolism; D045249:Sphingobacterium / Q000378:metabolism*
D025602:Halorhodopsins; D011994:Recombinant Proteins; D025604:Rhodopsins, Microbial; D025603:Sensory Rhodopsins