title: [Study of intermediate N using mutant forms of bacteriorhodopsin at Asp-96].
abstract: It has been found that the N(P, R)-type intermediate of the photocycle is formed in the Asp-96-->Asn mutant at acidic pH. Azide, which strongly activates the M decay in this mutant, allows the N intermediate to be shown also at neutral pH. Under these conditions mutant N decays in a pH-independent fashion. In the presence of azide, the H+ uptake by Asp-96-->Asn mutant bacteriorhodopsin follows the M decay, whereas the N decay occurs at a much slower rate. Two electrogenic stages have been shown to be associated with the M--->bR step in the Asp-96--->Asn mutant photocycle. The faster and slower stages correlate with the M--->N and N--->bR transitions, respectively. In the Asp-96--->Asn mutant, high concentrations of azide are found to increase the M decay rate up to the values higher than those in the wild-type protein, both with or without azide. Such an effect is absent for the Asp-96-->Glu mutant. The activation energies for M--->N and N--->bR transitions in the wild-type protein are equal to 18 and 19 kcal x mole-1, respectively. In the Asp-96-->Asn mutant without azide, the activation energy of the M decay is only 5 kcal x mole-1, whereas in the presence of azide in this mutant the activation energies for M and N decays are 8 and 9 kcal x mole-1, respectively. A scheme of events accompanying the Schiff base reprotonation during the photocycle is discussed.
authors.forename: S V
authors.initials: SV
authors.lastname: Danshina
authors.forename: L A
authors.initials: LA
authors.lastname: Drachev
authors.forename: A D
authors.initials: AD
authors.lastname: Kaulen
authors.forename: Kh G
authors.initials: KhG
authors.lastname: Korana
authors.forename: T
authors.initials: T
authors.lastname: Marti
authors.forename: T
authors.initials: T
authors.lastname: Mogi
authors.forename: V I
authors.initials: VI
authors.lastname: Skulachev
mesh_terms: D001224:Aspartic Acid / Q000235:genetics*; D001436:Bacteriorhodopsins / Q000235:genetics*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009154:Mutation; D011522:Protons
chemical_list: D011522:Protons; D001224:Aspartic Acid; D001436:Bacteriorhodopsins
vernacular_title: Issledovanie intermediatea N s pomoshch'iu mutantnykh form bakteriorhodopsina po Asp-96.