Characterization of a signaling complex composed of sensory rhodopsin I and its cognate transducer protein from the eubacterium Salinibacter ruber

Biochemistry. 2009 Oct 27;48(42):10136-45. doi: 10.1021/bi901338d.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Binding Sites
  • Halobacterium salinarum / metabolism
  • Halorhodopsins / chemistry
  • Light Signal Transduction*
  • Models, Molecular
  • Protein Conformation
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Rhodopsins, Microbial / chemistry*
  • Rhodopsins, Microbial / metabolism
  • Sensory Rhodopsins / chemistry*
  • Sensory Rhodopsins / metabolism
  • Sphingobacterium / metabolism*

Substances

  • Halorhodopsins
  • Recombinant Proteins
  • Rhodopsins, Microbial
  • Sensory Rhodopsins