title: Primary reaction of sensory rhodopsin II mutant D75N and the influence of azide.
abstract: The early steps in the photocycle of sensory rhodopsin II mutant D75N are investigated in a comprehensive study using femtosecond visible pump/probe spectroscopy. An overall slower response dynamics after photoexcitation is observed compared to wild-type sensory rhodopsin II, which is assigned to changed electrostatics and an altered hydrogen-bonding network within the retinal binding pocket. Furthermore, the influence of azide on the primary reaction is analyzed. The addition of azide accelerates the sub-10 ps dynamics of the D75N mutant nearly to reaction rates found in wild-type. Moreover, a further reaction pathway becomes observable in the investigated time range, which is assigned to a previously described K(1) to K(2) transition. The specific acceleration of the early steps seems to be a unique feature of the D75N mutant as similar azide effects do not emerge in analogous azide measurements of wild-type sensory rhodopsin II, bacteriorhodopsin, and the bacteriorhodopsin mutant D85N.
authors.affiliation: Institute of Physical and Theoretical Chemistry, Institute of Biophysics, Johann Wolfgang Goethe-University Frankfurt, Max von Laue-Strasse 7, 60438 Frankfurt am Main, Germany.
authors.forename: Mirka-Kristin
authors.initials: MK
authors.lastname: Verhoefen
authors.forename: Martin O
authors.initials: MO
authors.lastname: Lenz
authors.forename: Sergiu
authors.initials: S
authors.lastname: Amarie
authors.forename: Johann P
authors.initials: JP
authors.lastname: Klare
authors.forename: Jörg
authors.initials: J
authors.lastname: Tittor
authors.forename: Dieter
authors.initials: D
authors.lastname: Oesterhelt
authors.forename: Martin
authors.initials: M
authors.lastname: Engelhard
authors.forename: Josef
authors.initials: J
authors.lastname: Wachtveitl
mesh_terms: D001216:Asparagine / Q000235:genetics; D001224:Aspartic Acid / Q000235:genetics; D001386:Azides / Q000494:pharmacology*; D001436:Bacteriorhodopsins / Q000737:chemistry; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D006216:Halobacteriaceae / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D025602:Halorhodopsins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006860:Hydrogen Bonding / Q000187:drug effects; D057927:Hydrophobic and Hydrophilic Interactions; D009154:Mutation; D011522:Protons; D012545:Schiff Bases / Q000737:chemistry; D025603:Sensory Rhodopsins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D001386:Azides; D025602:Halorhodopsins; D011522:Protons; D012545:Schiff Bases; D025603:Sensory Rhodopsins; C061508:sensory rhodopsin II protein, archaeal; D001224:Aspartic Acid; D001436:Bacteriorhodopsins; D001216:Asparagine