Selective reaction of hydroxylamine with chromophore during the photocycle of pharaonis phoborhodopsin

Masayuki Iwamoto, Yuki Sudo, Kazumi Shimono, Naoki Kamo

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)


Phoborhodopsin (pR; also called sensory rhodopsin II, sRII) is a receptor of negative phototaxis of Halobacterium salinarum, and pharaonis phoborhodopsin (ppR; also pharaonis sensory rhodopsin II, psRII) is a corresponding protein of Natronobacterium pharaonis. These receptors contain retinal as a chromophore which binds to a lysine residue via Schiff base. This Schiff base can be cleaved with hydroxylamine to loose their color (bleaching). In dark, the bleaching rate of ppR was very slow whereas illumination accelerated considerably the bleaching rate. Addition of azide accelerated the decay of the M-intermediate while its formation (decay of the L-intermediate) is not affected. The bleaching rate of ppR under illumination was decreased by addition of azide. Essentially no reactivity with hydroxylamine under illumination was observed in the case of D75N mutant which lacks the M-intermediate in its photocycle. Moreover, we provided illumination by flashes to ppR in the presence of varying concentrations of azide to measure the bleaching rate per one flash. A good correlation was obtained between the rate and the mean residence time, MRT, which was calculated from flash photolysis data of the M-decay. These findings reveal that water-soluble hydroxylamine reacts selectively with the M-intermediate and its implication was discussed.

Original languageEnglish
Pages (from-to)152-158
Number of pages7
JournalBiochimica et Biophysica Acta - Biomembranes
Issue number1
Publication statusPublished - Sep 3 2001
Externally publishedYes


  • Bacteriorhodopsin
  • Bleach of chromophore
  • M-Intermediate
  • Natronobacterium pharaonis
  • Pharaonis sensory rhodopsin II

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology


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