ハロロドプシン-光により駆動される塩素イオンポンプ

概要

論文の詳細を見る
Spectroscopic, photochemical and biochemical properties of halorhodopsin are summarized. Halorhodopsin is present in the plasma membrane of Halobacterium halobium and acts as a light-driven Cl--pump. Halorhodopsin has an all-trans retinal as its chromophore which binds to apoprotein, halo-opsin through a protonated Schiff base. The absorption spectrum of halorhodopsin and its photoreaction depend on the chloride concentration in the medium. The λmax of halorhodopsin in the presence and absence of NaCl are 576 and 567 nm, respectively. The Cl--dependency of the absorption spectrum suggests the existence of two sites for binding Cl-; one is a “Cl--binding site” specific for Cl- and the other is an “anionbinding site” non-specific for Cl-. The Cl--binding site is responsible for the wavelength regulation of the absorption spectrum, while the anion-binding site is not. On the basis of these two binding sites, a light-driven Cl--pump mechanism has been suggested as follows : During the photoreaction of halorhodopsin, a Cl- is released from the Cl--binding site to the inside of the cell, then another Cl- in the anionbinding site shifts to the Cl--binding site and finally a Cl- in the medium outside of the cell is bound in the anion-binding site. Thus one Cl- in the medium can be transported into the inside of the cell by the aid of the photoreaction of one halorhodopsin molecule.
日本膜学会の論文