Association of pharaonis phoborhodopsin with its cognate transducer decreases the photo-dependent reactivity by water-soluble reagents of azide and hydroxylamine

Yuki Sudo, Masayuki Iwamoto, Kazumi Shimono, Naoki Kamo

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28 Citations (Scopus)


pharaonis phoborhodopsin (ppR; also pharaonis sensory rhodopsin II, psRII) is a receptor of the negative phototaxis of Natronobacterium pharaonis. In halobacterial membrane, ppR forms a complex with its transducer pHtrII, and this complex transmits the light signal to the sensory system in the cytoplasm. In the present work, the truncated transducer, t-Htr, was used which interacts with ppR [Sudo et al. (2001) Photochem. Photobiol. 74, 489-494]. Two water-soluble reagents, hydroxylamine and azide, reacted both with the transducer-free ppR and with the complex ppR/t-Htr (the complex between ppR and its truncated transducer). In the dark, the bleaching rates caused by hydroxylamine were not significantly changed between transducer-free ppR and ppR/t-Htr, or that of the free ppR was a little slower. Illumination accelerated the bleach rates, which is consistent with our previous conclusion that the reaction occurs selectively at the M-intermediate, but the rate of the complex was about 7.4-fold slower than that of the transducer-free ppR. Azide accelerated the M-decay, and its reaction rate of ppR/t-Htr was about 4.6-fold slower than free ppR. These findings suggest that the transducer binding decreases the water accessibility around the chromophore at the M-intermediate. Its implication is discussed.

Original languageEnglish
Pages (from-to)63-69
Number of pages7
JournalBBA - Biomembranes
Issue number1
Publication statusPublished - Jan 2 2002
Externally publishedYes



  • Bleach of retinoid protein
  • Flash photolysis
  • Halobacterium salinarum
  • Natronobacterium pharaonis
  • Sensory rhodopsin

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Cell Biology

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