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Effects of Three Characteristic Amino Acid Residues of Pharaonis Phoborhodopsin on the Absorption Maximum ¶
Author(s) -
Shimono Kazumi,
Iwamoto Masayuki,
Sumi Masato,
Kamo Naoki
Publication year - 2000
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/0031-8655(2000)0720141eotcaa2.0.co2
Subject(s) - bacteriorhodopsin , mutant , amino acid , rhodopsin , halobacteriaceae , chemistry , stereochemistry , crystallography , biology , biophysics , biochemistry , membrane , gene , halobacterium salinarum , retinal
Phoborhodopsin (pR or sensory rhodopsin II, sRII) or pharaonis phoborhodopsin ( p pR or pharaonis sensory rhodopsin II, p sRII) has a unique absorption maximum (λ max ) compared with three other archaeal rhodopsins: λ max of pR or p pR at ca 500 nm and others at 560–590 nm. Alignment of amino acid sequences revealed three sites characteristic of the shorter wavelength–absorbing pigments. The amino acids of these three sites are conserved completely among archaeal rhodopsins having longer λ max , and are different from those of pR or p pR. We replaced these amino acids of p pR with amino acids corresponding to those of bacteriorhodopsin, Val‐108 to Met, Gly‐130 to Ser and Thr‐204 to Ala. The λ max of V108M mutant was 502 nm with a slight redshift. G130S and T204A mutants had λ max of 503 and 508 nm, respectively. Thus, each site contributes only a small effect to the color tuning. We then constructed three double mutants and one triple mutant. The opsin‐shifts of these mutants suggest that Val‐108 and Thr‐204 or Gly‐130 are synergistic, and that Gly‐130 and Thr‐204 work additively. Even in the triple mutant, the λ max was 515 nm, an opsin‐shift only ca 30% of the shift value from 500 to 560 nm. This means that there is another yet unidentified factor responsible for the color tuning.