title: Interaction of Natronobacterium pharaonis phoborhodopsin (sensory rhodopsin II) with its cognate transducer probed by increase in the thermal stability.
abstract: Pharaonis phoborhodopsin (ppR, also called Natronobacterium pharaonis sensory rhodopsin II) and its transducer protein, pharaonis halobacterial transducer of ppR (pHtrII), form a signaling complex, and light signals are transmitted from the sensor to the transducer by the protein-protein interaction. A truncated pHtrII(1-159) consisting of intramembrane helices (expressing amino acid residues from the first to the 159th position) and ppR form the complex in a solution containing 0.1% n-dodecyl-beta-D-maltoside. At 75-85 degrees C, the time-dependent color loss of ppR was caused by denaturation. We found that pHtrII(1-159) retarded the denaturation rate of ppR. This increase in the thermal stability was used as a probe for the binding ability in the dark. Tyr199 of ppR and Asn74 of pHtrII(1-114) were proposed as amino acid residues interacting with each other through hydrogen bonding. Then,ppR and pHtrII(1-159) mutants at these positions were prepared to examine the effect on the binding in the dark. The wild-type and Y199F mutant can bind pHtrII(1-159), suggesting that the hydrogen bonding between these specific amino acid residues may not be the only cause of the binding, but the hydrophobic interaction via phenyl ring of ppR may contribute dominantly.
authors.affiliation: Laboratory of Biophysical Chemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Sudo
authors.forename: Masaki
authors.initials: M
authors.lastname: Yamabi
authors.forename: Masayuki
authors.initials: M
authors.lastname: Iwamoto
authors.forename: Kazumi
authors.initials: K
authors.lastname: Shimono
authors.forename: Naoki
authors.initials: N
authors.lastname: Kamo
mesh_terms: D019843:Archaeal Proteins / Q000378:metabolism*; D002338:Carotenoids / Q000378:metabolism*; D025602:Halorhodopsins; D006860:Hydrogen Bonding; D019633:Natronobacterium / Q000737:chemistry*; D011485:Protein Binding; D025603:Sensory Rhodopsins; D013057:Spectrum Analysis
chemical_list: D019843:Archaeal Proteins; D025602:Halorhodopsins; D025603:Sensory Rhodopsins; C061508:sensory rhodopsin II protein, archaeal; D002338:Carotenoids