Transducer binding establishes localized interactions to tune sensory rhodopsin II.
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.
Cisneros
David A
DA
Biotechnology Center, University of Technology, Dresden, Germany.
Oberbarnscheidt
Leoni
L
Pannier
Angela
A
Klare
Johann P
JP
Helenius
Jonne
J
Engelhard
Martin
M
Oesterhelt
Filipp
F
Muller
Daniel J
DJ
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*
D019843:Archaeal Proteins; D025602:Halorhodopsins; D025603:Sensory Rhodopsins; C061508:sensory rhodopsin II protein, archaeal