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Role of Arg-72 of pharaonis Phoborhodopsin (sensory rhodopsin II) on its photochemistry.

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Title: Role of Arg-72 of pharaonis Phoborhodopsin (sensory rhodopsin II) on its photochemistry.
Authors: Ikeura, Yukako Browse this author
Shimono, Kazumi Browse this author
Iwamoto, Masayuki Browse this author
Sudo, Yuki Browse this author
Kamo, Naoki Browse this author
Keywords: pKa of the counterion of the Schiff base
M-decay rate
M-formation rate
Proton uptake and release
Proton releasing group
Issue Date: May-2004
Publisher: The Biophysical Society
Journal Title: Biophysical Journal
Volume: 86
Issue: 5
Start Page: 3112
End Page: 3120
PMID: 15111424
Abstract: Pharaonis phoborhodopsin (ppR, or pharaonis sensory rhodopsin II, NpsRII) is a sensor for the negative phototaxis of Natronomonas (Natronobacterium) pharaonis. Arginine 72 of ppR corresponds to Arg-82 of bacteriorhodopsin, which is a highly conserved residue among microbial rhodopsins. Using various Arg-72 ppR mutants, we obtained the following results: 1), Arg-72ppR together possibly with Asp-193 influenced the pKa of the counterion of the protonated Schiff base. 2), The M-rise became approximately four times faster than the wild-type. 3), Illumination causes proton uptake and release, and the pH profiles of the sequence of these two proton movements were different between R72A mutant and the wild-type; it is inferred that Arg-72 connects the proton transfer events occurring at both the Schiff base and an extracellular proton-releasing residue (Asp-193). 4), The M-decays of Arg-72 mutants were faster (8–27 folds at pH 8 depending on mutants) than the wild-type, implying that the guanidinium prevents the proton transfer from the extracellular space to the deprotonated Schiff base. 5), The proton-pumping activities were decreased for mutants having increased M-decay rates, but the extent of the decrease was smaller than expected. The role of Arg-72 of ppR on the photochemistry was discussed.
Type: article (author version)
Appears in Collections:薬学研究院 (Faculty of Pharmaceutical Sciences) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 加茂 直樹

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