FORMATION AND PROPERTIES OF BACTERIORHODOPSIN MONOMERS IN NONIONIC DETERGENTS OCTYL-BETA-GLUCOSIDE AND TRITON X-100
FORMATION AND PROPERTIES OF BACTERIORHODOPSIN MONOMERS IN NONIONIC DETERGENTS OCTYL-BETA-GLUCOSIDE AND TRITON X-100
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DOI：
10.1016/0014-5793(78)80427-x
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发表时间：
1978-01-01
期刊：
影响因子：
3.5
通讯作者：
HEYN, MP
中科院分区：
文献类型：
--
作者：
DENCHER, NA;HEYN, MP
由于盐生盐杆菌紫膜的细菌视紫红质分子排列在一个二维的六角晶格的三聚体，蛋白质-蛋白质相互作用可能会影响其结构和功能（例如，泵率）。因此，为了比较细菌视紫红质在聚集状态和单体状态下的性质，可逆地解聚细菌视紫红质是有意义的。已经表明，可见圆二色性（CD）光谱中的激子耦合效应可以用于监测细菌视紫红质的聚集状态并区分单体和聚集的细菌视紫红质[1 -5]。激子CD偶联体由在约535 nm处具有最大值的正带和在约600 nm处具有极值的负带组成，并且仅当存在特定的细菌视紫红质聚集体时才发生。在含有磷脂酰胆碱囊泡的细菌视紫红质中，可以通过降低温度来诱导细菌视紫红质的可逆聚集[S]。而蛋白质的六方聚集状态的特征在于激子CD光谱，单体状态的特征在于以吸收最大值为中心的正CD带[5]。在单体视紫红质中也观察到类似的“单体”或固有CD带[6]。基于激子CD带的消失，表明细菌视紫红质在Triton X-100和辛基-OD-葡萄糖苷中的增溶导致蛋白质单体的形成。这些观察结果得到了离心实验和旋转螺旋桨测量的支持。
Since the bacteriorhodopsin molecules of the purple membrane of Halobacterium halobium are arranged in a two-dimensional hexagonal lattice of trimers, protein-protein interactions may well affect its structure and function (eg, the pumping rate). It is therefore of interest to reversibly disaggregate bacteriorhodopsin in order to compare its properties in the aggregated and in the monomeric state. It has been shown that the exciton coupling effects in the visible circular dichroism (CD) spectra can be used to monitor the state of aggregation of bacteriorhodopsin and to distinguish between monomeric and aggregated bacteriorhodopsin[l-5]. The exciton CD couplet consists of a positive band with maximum at about 535 nm and a negative band with extremum at about 600 nm and occurs only if specific bacteriorhodopsin aggregates are present. In bacteriorhodopsin containing phosphatidylcholine vesicles, reversible aggregation of bacteriorhodopsin can be induced by lowering the temperature [S]. Whereas the hexagonally aggregated state of the protein is characterized by an exciton CD spectrum, the monomeric state is characterized by a positive CD band centered at the absorption maximum [5]. A similar ‘monomer’or intrinsic CD band is also observed with monomeric rhodopsin [6].It is shown on the basis of the disappearance of the exciton CD bands that solubilization of bacteriorhodopsin in Triton X-100 and octyl-OD-glucoside leads to the formation of protein monomers. These observations are supported by centrifugation experiments and by measurements of the rotational correla-