title: Association between a photo-intermediate of a M-lacking mutant D75N of pharaonis phoborhodopsin and its cognate transducer.
abstract: Pharaonis phoborhodopsin (ppR or pharaonis sensory rhodopsin II) is a receptor of the negative phototaxis of Natronobacterium pharaonis and forms a complex with its transducer pHtrII in membranes. Flash-photolyis of a D75N mutant did not yield the M-intermediate, but an O-like intermediate is observed in a ms time range. We examined the interaction between the D75N of ppR and t-Htr (truncated pHtrII). These formed a complex in the presence of 0.1% n-dodecyl-beta-maltoside, and the association accelerated the decay of the O of D75N from 15 to 56 s(-1). From the decay time constants under varying ratios of D75N and t-Htr, n, the molar ratio of D75N/t-Htr in the complex, and K(D), the dissociation constant, were estimated. The value of n was unity and K(D) was estimated to 146 nM. This K(D) value can be considered to be the association between the photo-intermediate and t-Htr, which is deduced by the method of estimation. Previously we (Photochem. Photobiol. 74 (2001) 489) reported a K(D) of 15 microM for the interaction between the wild-type and t-Htr by means of the change in M-decay rates. Therefore, this value should be the K(D) value for the interaction between M of the wild-type and t-Htr.
authors.affiliation: Laboratory of Biophysical Chemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Sudo
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 / Q000737:chemistry* / Q000235:genetics; D002338:Carotenoids / Q000737:chemistry* / Q000235:genetics; D025602:Halorhodopsins; D009154:Mutation; D010777:Photochemistry; D010957:Plasmids; D025603:Sensory Rhodopsins
chemical_list: D019843:Archaeal Proteins; D025602:Halorhodopsins; D025603:Sensory Rhodopsins; C061508:sensory rhodopsin II protein, archaeal; D002338:Carotenoids