Transducer Binding Establishes Localized Interactions to Tune Sensory Rhodopsin II

• Published in: Structure (London) Vol. 16; no. 8; pp. 1206 - 1213
• Main Authors: Cisneros, David A., Oberbarnscheidt, Leoni, Pannier, Angela, Klare, Johann P., Helenius, Jonne, Engelhard, Martin, Oesterhelt, Filipp, Muller, Daniel J.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 06-08-2008
• Subjects: Archaeal Proteins - chemistry; CELLBIO; Halobacteriaceae - chemistry; Halorhodopsins - chemistry; Models, Molecular; Protein Binding; Protein Conformation; Sensory Rhodopsins - chemistry; SIGNALING; Spectrum Analysis - methods; CELLBIO; SIGNALING
• ISSN: 0969-2126; 1878-4186; 1878-4186
• DOI: 10.1016/j.str.2008.04.014

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 α helices F and G of NpSRII to which the transducer was in contact. Remarkably, the interactions were distributed asymmetrically and significantly stabilized α helix G entirely but α 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.