title: Pharaonis phoborhodopsin binds to its cognate truncated transducer even in the presence of a detergent with a 1:1 stoichiometry.
abstract: Pharaonis phoborhodopsin (ppR) (also pharaonis sensory rhodopsin II) is a receptor of the negative phototaxis of Natronobacterium pharaonis. ppR forms a complex with its pharaonis halobacterial transducer (pHtrII), and this complex transmits the light signal to the sensory system in the cytoplasm. The expressed C-terminal-His tagged ppR and C-terminal-His tagged truncated pHtrII (t-Htr) in Escherichia coli (His means the 6x histidine tag) form a complex even in the presence of 0.1% of n-dodecyl-beta-D-maltoside, and the M-decay of the complex became about twice slower than that of ppR alone. The photocycling rates under varying concentration ratios of ppR to t-Htr in the presence of detergent were measured. The data were analyzed on the following assumptions: (1) the M-decay of both ppR alone and the complex followed a single exponential decay with different time constants; and (2) the M-decay under varying concentration ratios of ppR to t-Htr, therefore, followed a biexponential decay function which combined the decay of the free ppR and that of the complex as photoreactive species. From these analyses we estimated the dissociation constant (15.2 +/- 1.8 microM) and the number of binding sites (1.2 +/- 0.08).
authors.affiliation: Laboratory of Biophysical Chemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Sudo
authors.forename: M
authors.initials: M
authors.lastname: Iwamoto
authors.forename: K
authors.initials: K
authors.lastname: Shimono
authors.forename: N
authors.initials: N
authors.lastname: Kamo
mesh_terms: D019843:Archaeal Proteins / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D001665:Binding Sites; D002338:Carotenoids / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D025602:Halorhodopsins; D007700:Kinetics; D019633:Natronobacterium / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D018462:Photobiology; D020283:Photoreceptors, Microbial / Q000378:metabolism / Q000528:radiation effects; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D025603:Sensory Rhodopsins
chemical_list: D019843:Archaeal Proteins; D025602:Halorhodopsins; D020283:Photoreceptors, Microbial; D011994:Recombinant Proteins; D025603:Sensory Rhodopsins; C061508:sensory rhodopsin II protein, archaeal; D002338:Carotenoids