Walz T, Ghosh R
Maurice-Müller Institute for Microscopic Structural Biology, Biozentrum, Universität Basel, Switzerland.
J Mol Biol. 1997 Jan 17;265(2):107-11. doi: 10.1006/jmbi.1996.0714.
A stoichiometric unit of the light-harvesting complex I and the reaction centre (LHI-RC complex) has been isolated from a carotenoid-less mutant of the purple non-sulphur bacterium Rhodospirillum rubrum by mild solubilization of photosynthetic membranes with the phospholipid detergent diheptylphosphatidylcholine. Dialysis of the isolated LHI-RC complexes in the presence of added dioleoyl-sn-phosphatidylcholine produced ordered two-dimensional crystals. Digital image processing revealed that the LHI-RC are packed together in a square lattice (a = b = 16.3 nm). The dimensions of the LHI ring are essentially identical with those determined from two-dimensional (2D) crystals of purified carotenoid-containing light-harvesting I complexes after analysis by cryo-electron microscopic techniques or from negatively stained 2D crystals of purified LHI complexes from a carotenoid-less mutant. Each LHI ring of the LHI-RC complex contains a central diffuse stain-excluding region, which is assigned to the reaction centre. The analysis of the LHI-RC 2D crystals strongly suggests that the geometry and subunit stoichiometry of the LHI ring is unaffected by the presence of a reaction centre that can probably assume various orientations within the ring.
通过用磷脂洗涤剂二庚基磷脂酰胆碱对光合膜进行温和增溶，从紫色非硫细菌红螺菌的无类胡萝卜素突变体中分离出了光捕获复合物I和反应中心的化学计量单元（LHI-RC复合物）。在添加二油酰-sn-磷脂酰胆碱的情况下对分离出的LHI-RC复合物进行透析，产生了有序的二维晶体。数字图像处理显示，LHI-RC以正方形晶格（a = b = 16.3 nm）排列在一起。LHI环的尺寸与通过低温电子显微镜技术分析后从纯化的含类胡萝卜素的光捕获I复合物的二维（2D）晶体中确定的尺寸基本相同，或者与从无类胡萝卜素突变体的纯化LHI复合物的负染色2D晶体中确定的尺寸基本相同。LHI-RC复合物的每个LHI环都包含一个中央弥散的无染色区域，该区域被指定为反应中心。对LHI-RC二维晶体的分析强烈表明，LHI环的几何形状和亚基化学计量不受反应中心存在的影响，反应中心可能在环内呈现各种取向。
