title: Transducer binding establishes localized interactions to tune sensory rhodopsin II.
abstract: In haloarchaea, sensory rhodopsin II (SRII) mediates a photophobic response to avoid photo-oxidative damage in bright light. Upon light activation the receptor undergoes a conformational change that activates a tightly bound transducer molecule (HtrII), which in turn by a chain of homologous reactions transmits the signal to the chemotactic eubacterial two-component system. Here, using single-molecule force spectroscopy, we localize and quantify changes to the intramolecular interactions within SRII of Natronomonas pharaonis (NpSRII) upon NpHtrII binding. Transducer binding affected the interactions at transmembrane alpha helices F and G of NpSRII to which the transducer was in contact. Remarkably, the interactions were distributed asymmetrically and significantly stabilized alpha helix G entirely but alpha helix F only at its extracellular tip. These findings provide unique insights into molecular mechanisms that "prime" the complex for signaling, and guide the receptor toward transmitting light-activated structural changes to its cognate transducer.
authors.affiliation: Biotechnology Center, University of Technology, Dresden, Germany.
authors.forename: David A
authors.initials: DA
authors.lastname: Cisneros
authors.forename: Leoni
authors.initials: L
authors.lastname: Oberbarnscheidt
authors.forename: Angela
authors.initials: A
authors.lastname: Pannier
authors.forename: Johann P
authors.initials: JP
authors.lastname: Klare
authors.forename: Jonne
authors.initials: J
authors.lastname: Helenius
authors.forename: Martin
authors.initials: M
authors.lastname: Engelhard
authors.forename: Filipp
authors.initials: F
authors.lastname: Oesterhelt
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Muller
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry*; D006216:Halobacteriaceae / Q000737:chemistry; D025602:Halorhodopsins / Q000737:chemistry*; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D025603:Sensory Rhodopsins / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods*
chemical_list: D019843:Archaeal Proteins; D025602:Halorhodopsins; D025603:Sensory Rhodopsins; C061508:sensory rhodopsin II protein, archaeal