Single-molecule force spectroscopy measures structural changes induced by light activation and transducer binding in sensory rhodopsin II.
Microbial rhodopsins are a family of seven-helical transmembrane proteins containing retinal as chromophore. Sensory rhodopsin II (SRII) triggers two very different responses upon light excitation, depending on the presence or the absence of its cognate transducer HtrII: Whereas light activation of the NpSRII/NpHtrII complex activates a signalling cascade that initiates the photophobic response, NpSRII alone acts as a proton pump. Using single-molecule force spectroscopy, we analysed the stability of NpSRII and its complex with the transducer in the dark and under illumination. By improving force spectroscopic data analysis, we were able to reveal the localisation of occurring forces within the protein chain with a resolution of about six amino acids. Distinct regions in helices G and F were affected differently, depending on the experimental conditions. The results are generally in line with previous data on the molecular stability of NpSRII. Interestingly, new interaction sites were identified upon light activation, whose functional importance is discussed in detail.
Oberbarnscheidt
Leoni
L
Institut für molekulare physikalische Chemie, Düsseldorf, Germany.
Janissen
Richard
R
Martell
Swetlana
S
Engelhard
Martin
M
Oesterhelt
Filipp
F
D019843:Archaeal Proteins / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D002338:Carotenoids / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D025602:Halorhodopsins / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D008958:Models, Molecular; D019633:Natronobacterium / Q000737:chemistry; D055668:Photochemical Processes; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism / Q000528:radiation effects; D025603:Sensory Rhodopsins / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D015398:Signal Transduction; D013057:Spectrum Analysis
D019843:Archaeal Proteins; D025602:Halorhodopsins; C434451:HtrII protein, Natronobacterium pharaonis; D011994:Recombinant Proteins; D025603:Sensory Rhodopsins; C434450:phototaxis receptor sensory rhodopsin II, Natronobacterium pharaonis; C061508:sensory rhodopsin II protein, archaeal; D002338:Carotenoids