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Role of Asp193 in chromophore-protein interaction of pharaonis phoborhodopsin (sensory rhodopsin II).

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Title: Role of Asp193 in chromophore-protein interaction of pharaonis phoborhodopsin (sensory rhodopsin II).
Authors: Iwamoto, Masayuki Browse this author
Furutani, Yuji Browse this author
Sudo, Yuki Browse this author
Shimono, Kazumi Browse this author
Kandori, Hideki Browse this author
Kamo, Naoki Browse this author
Keywords: hydrogen bonding network
anion binding
pKa of Schiff base
spectroscopic titration
sensory rhodopsin II
archaeal rhodopsin
Issue Date: Aug-2002
Publisher: The Biophysical Society
Journal Title: Biophysical Journal
Volume: 83
Issue: 2
Start Page: 1130
End Page: 1135
PMID: 12124292
Abstract: Pharaonis phoborhodopsin (ppR; also pharaonis sensory rhodopsin II, psRII) is a receptor of the negative phototaxis of Natronobacterium pharaonis. By spectroscopic titration of D193N and D193E mutants, the pKa of the Schiff base was evaluated. Asp193 corresponds to Glu204 of bacteriorhodopsin (bR). The pKa of the Schiff base (SBH+) of D193N was ~10.1-10.0 (at XH+) and ~11.4-11.6 (at X) depending on the protonation state of a certain residue (designated by X) and independent of Cl, whereas those of the wild type and D193E were >12. The pKa values of XH+ were ~11.8-11.2 at the state of SB, 10.5 at SBH+ state in the presence of Cl, and 9.6 at SBH+ without Cl. These imply the presence of a long-range interaction in the extracellular channel. Asp193 was suggested to be deprotonated in the present dodecyl-maltoside (DDM) solubilized wild-type ppR, which is contrary to Glu204 of bR. In the absence of salts, the irreversible denaturation of D193N (but not the wild type and D193E) occurred via a metastable state, into which the addition of Cl reversed the intact pigment. This suggests that the negative charge at residue 193, which can be substituted by Cl, is necessary to maintain the proper conformation in the DDM-solubilized ppR.
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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