Environment around the chromophore in pharaonis phoborhodopsin: Mutation analysis of the retinal binding site

Kazumi Shimono, Yukako Ikeura, Yuki Sudo, Masayuki Iwamoto, Naoki Kamo

Research output: Contribution to journalArticlepeer-review

71 Citations (Scopus)


Phoborhodopsin (pR or sensory rhodopsin II, sRII) and pharaonis phoborhodopsin (ppR or pharaonis sRII, psRII) have a unique absorption maximum (λmax) compared with three other archaeal rhodopsins: λmax of pR and ppR is approx. 500 nm and of others (e.g. bacteriorhodopsin, bR) is 560-590 nm. To determine the residue contributing to the opsin shift from ppR to bR, we constructed various ppR mutants, in which a single residue was substituted for a residue corresponding to that of bR. The residues mutated were those which differ from that of bR and locate within 5 Å from the conjugated polyene chain of the chromophore or any methyl group of the polyene chain. The shifts of λmax of all mutants were small, however. We constructed a mutant in which all residues which differ from those of bR in the retinal binding site were simultaneously substituted for those of bR, but the shift was only from 499 to 509 nm. Next, we constructed a mutant in which 10 residues located within 5 Å from the polyene as described above were simultaneously substituted. Only 44% of the opsin shift (λmax of 524 nm) from ppR to bR was obtained even when all amino acids around the chromophore were replaced by the same residues as bR. We therefore conclude that the structural factor is more important in accounting for the difference of λmax between ppR and bR rather than amino acid substitutions. The possible structural factors are discussed.

Original languageEnglish
Pages (from-to)92-100
Number of pages9
JournalBiochimica et Biophysica Acta - Biomembranes
Issue number2
Publication statusPublished - Dec 1 2001
Externally publishedYes


  • Absorption maximum
  • Natronobacterium pharaonis
  • Opsin shift
  • Pharaonis sensory rhodopsin II
  • Site-directed mutagenesis

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology


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