title: Solid-state NMR and functional studies on proteorhodopsin.
abstract: Proteins of the proteorhodopsin (PR) family are found abundantly in many marine bacteria in the photic zone of the oceans. They are colour-tuned to their environment. The green absorbing species has been shown to act as a light-driven proton pump and thus could form a potential source of energy. The pK(a) of the primary proton acceptor is close to the pH of seawater which could also indicate a regulatory role. Here, we review and summarize our own recent findings in the context of known data and present some new results. Proton transfer in vitro by PR is shown by a fluorescence assay which confirms a pH dependent vectoriality. Previously reported low diffracting 2D crystal preparations of PR are assessed for their use for solid-state NMR by two dimensional (13)C-(13)C DARR spectra. (15)N-(1)H HETCOR MAS NMR experiments show bound water in the vicinity of the protonated Schiff base which could play a role in proton transfer. The effect of highly conserved H75 onto the properties of the chromophore has been investigated by single site mutations. They do show a pronounced effect onto the optical absorption maximum and the pK(a) of the proton acceptor but have only a small effect onto the (15)N chemical shifts of the protonated Schiff base.
authors.affiliation: Institute for Biophysical Chemistry, Goethe University Frankfurt, Max von Laue Str. 9, 60438 Frankfurt/M., Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Pfleger
authors.forename: Andreas C
authors.initials: AC
authors.lastname: Wörner
authors.forename: Jun
authors.initials: J
authors.lastname: Yang
authors.forename: Sarika
authors.initials: S
authors.lastname: Shastri
authors.forename: Ute A
authors.initials: UA
authors.lastname: Hellmich
authors.forename: Lubica
authors.initials: L
authors.lastname: Aslimovska
authors.forename: Melanie S M
authors.initials: MS
authors.lastname: Maier
authors.forename: Clemens
authors.initials: C
authors.lastname: Glaubitz
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D020285:Cryoelectron Microscopy; D006639:Histidine / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D018625:Microscopy, Atomic Force; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D019906:Nuclear Magnetic Resonance, Biomolecular; D055668:Photochemical Processes; D011522:Protons; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D012243:Rhodopsin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D025604:Rhodopsins, Microbial; D017386:Sequence Homology, Amino Acid; D013053:Spectrophotometry
chemical_list: D011522:Protons; D011994:Recombinant Proteins; D025604:Rhodopsins, Microbial; C413548:proteorhodopsin; D006639:Histidine; D012243:Rhodopsin