title: Acetabularia rhodopsin I is a light-stimulated proton pump.
abstract: We cloned an intronless, nuclear-encoded opsin gene from an EST library of Acetabularia acetabulum. Acetabularia rhodopsin I (ARI) encodes a protein of 246 amino acids with molecular weight of 27 kDa. ARI was reconstituted in the Xenopus oocyte expression system to characterize its electrophysiological properties utilizing the two-electrode voltage-clamping technique. Oocytes where ARI cRNA was injected displayed outward directed currents in response to light. The maximum action spectrum of ARI was detected at 520 nm green light. Light-stimulated ARI current amplitude was altered by the protons, but not by the other ions in recording solutions, suggesting that the algal rhodopsin is a light-stimulated proton pump. Typical proton-mediated outward current elicited by 520 nm light was characterized with two phases of non-inactivating outward current following initial transient current. Taken together, we here reported cloning of a novel Acetabularia opsin gene which was characterized to be a proton-pump stimulated by light.
authors.affiliation: Department of Life Science, Sogang University, Seoul 121-742, Republic of Korea.
authors.forename: Sang-Soo
authors.initials: SS
authors.lastname: Lee
authors.forename: Ah Reum
authors.initials: AR
authors.lastname: Choi
authors.forename: So Young
authors.initials: SY
authors.lastname: Kim
authors.forename: Ho-Won
authors.initials: HW
authors.lastname: Kang
authors.forename: Kwang-Hwan
authors.initials: KH
authors.lastname: Jung
authors.forename: Jung-Ha
authors.initials: JH
authors.lastname: Lee
mesh_terms: D000076:Acetabularia / Q000737:chemistry*; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D006801:Humans; D008027:Light; D017494:Proton Pumps / Q000737:chemistry*; D012243:Rhodopsin / Q000737:chemistry* / Q000235:genetics; D014981:Xenopus
chemical_list: D017931:DNA Primers; D017494:Proton Pumps; D012243:Rhodopsin