title: Regeneration and inhibition of proton pumping activity of bacteriorhodopsin blue membrane by cationic amine anesthetics.
abstract: Bacteriorhodopsin (bR) is the prototype of an integral membrane protein with seven membrane-spanning alpha-helices and serves as a model of the G-protein-coupled drug receptors. This study is aimed at reaching a greater understanding of the role of amine local anesthetic cations on the proton transport in the bR protein, and furthermore, the functional role of "the cation" in the proton pumping mechanism. The effect of the amine anesthetic cations on the proton pump in the bR blue membrane was compared with those by divalent (Ca2+, Mg2+ and Mn2+) and monovalent metal cations (Li+, Na+, K+ and Cs+), which are essential for the correct functioning of the proton pumping of the bR protein. The results suggest that the interacting site of the divalent cation to the bR membrane may differ from that of the monovalent metal cation. The electric current profile of the bR blue membrane in the presence of the amine anesthetic cations was biphasic, involving the generation and inhibition of the proton pumping activity in a concentration-dependent manner. The extent of the regeneration of the proton pump by the additives increased in the order of monovalent metal cation<monovalent amine anesthetic cation<divalent metal cation. We found that organic cations such as the amine anesthetics can also regenerate the proton pump in the bR protein. The inhibition of proton transport in the bR protein by the anesthetic cations was elucidated using the wild type, the E204Q and the D96N mutated bRs. The hydrophobic interaction of the amine anesthetics with the bR protein plays an important part in inhibiting the bR proton pump.
authors.affiliation: Faculty of Pharmaceutical Sciences, The University of Tokushima, Shomachi, Tokushima 770-8505, Japan. ashibata@ph.tokushima-u.ac.jp
authors.forename: Akira
authors.initials: A
authors.lastname: Shibata
authors.forename: Ayako
authors.initials: A
authors.lastname: Sakata
authors.forename: Satoru
authors.initials: S
authors.lastname: Ueno
authors.forename: Tsuguhide
authors.initials: T
authors.lastname: Hori
authors.forename: Kazushi
authors.initials: K
authors.lastname: Minami
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Baba
authors.forename: Naoki
authors.initials: N
authors.lastname: Kamo
mesh_terms: D000588:Amines / Q000494:pharmacology*; D000777:Anesthetics / Q000494:pharmacology*; D001436:Bacteriorhodopsins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002412:Cations; D002462:Cell Membrane / Q000187:drug effects*; D019617:Halobacterium salinarum / Q000187:drug effects; D054328:Proton Pump Inhibitors; D011522:Protons; D018717:Purple Membrane / Q000187:drug effects
chemical_list: D000588:Amines; D000777:Anesthetics; D002412:Cations; D054328:Proton Pump Inhibitors; D011522:Protons; D001436:Bacteriorhodopsins