Studies on Retinoid Proteins in Membranes of Halobacterium halobium

（1）我们的前期研究表明盐生盐杆菌（Halobacterium halobium）胞质膜上存在第四类视色素蛋白。我们将其命名为phoborhodopsin（简称pR）。本研究利用闪光光解技术揭示了pR的光循环。在照射时，形成在350 nm处吸收的光化学中间体，其在室温下以140 msec的半衰期转变为在530 nm处吸收的中间体。在530 nm处的中间吸收以约300 msec的半衰期衰减，并返回到原始pR。（2）H.盐被长波长光吸引，这种行为称为正趋光性。为了证明正趋光性的受体是感觉视紫红质（sR）的假说，我们仔细测量了正趋光性的作用光谱，并与sR的吸收光谱进行了比较，发现两者吻合得很好，支持了这一假说。（3）细菌视紫红质（bR）是一种蛋白质， ...更多信息 n在紫膜上。当介质的pH低于3.2或bR通过阳离子交换柱时，bR变为蓝色。我们发现，四（4-氟苯基）硼，亲脂性阴离子添加到bR形成蓝膜，即使在中性溶液中。向去离子蓝色膜中加入亲脂性阳离子使颜色恢复为紫色。分析表明，亲脂性离子结合的疏水区域的存在和该区域的电子电荷调节bR的颜色。（4）光驱动离子泵活性的测定方法之一。Halobium是用来测量光诱导膜电位的。对于小的细胞或囊泡，应采用间接法估算膜电位。亲脂性离子在细胞内外的分布经常被使用。估计值的模糊性已被提出，这是由亲脂性离子的结合引起的。我们开发了校正结合的方法来估计真实的膜电位。少

(1)Our previous study has shown the existence of the fourth retinoid protein in the cytoplasmic membrane of Halobacterium halobium. We named it as phoborhodopsin (abbreviated as pR). The present study revealed the photocycle of pR with use of flash-photolysis. Upon an illumination, a photochemical intermediate absorbing at 350 nm is formed, which transforms to an intermediate absorbing at 530 nm with a half time of 140 msec at room temperature. The intermediate absorbing at 530 nm decays with a half time of ca 300 msec and returns to the original pR.(2)H. halobium is attracted to the long wavelength light and this behavior is called positive photo-taxis. In order to prove the hypothesis that the receptor of positive photo-taxis is sensory rhodopsin (sR), we measured carefully the action spectrum of positive photo-taxis and compared it with the absorption spectrum of sR. The finding that both spectra agree well each other supported the hypothesis.(3)Bacteriorhodopsin (bR) is only protei … More n in purple membrane. When pH of the medium is lowered than 3.2 or when bR is passed through cation exchanger column, bR turns blue. We found that addition of tetrakis(4-fluorophenyl)boron, lipophilic anion to bR formed blue membrane even in neutral solutions. Addition of lipophilic cation to the deionized blue membrane restored the color to purple. Analysis suggested the existence of hydrophobic region where lipophilic ions bind and the electronic charges of this region regulate the color of bR.(4)One of ways for the estimation of activity of light-driven ion-pumps in the membrane of H. halobium is to measure the photo-induced membrane potential. For small cells or vesicles, indirect method of the estimation of membrane potential should be employed. Distribution of lipophilic ions inside and outside the cells are frequently used. Ambiguity of the estimated values has been suggested which are caused by the binding of lipophilic ions. We developed the method to correct the binding to estimate the true membrane potential. Less