聚光的晶体结构复杂二世(b800 - 850)从Rhodospirillum molischianum。
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Koepke J,胡锦涛X, Muenke C,舒尔腾K,米歇尔·H
聚光的晶体结构复杂二世(b800 - 850)从Rhodospirillum molischianum。
结构。1996年5月15日,4 (5):581 - 97。
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8736556 (在PubMed]
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背景:聚光复合体II (LH-2s)积分形成环状结构的膜蛋白,低聚物的αbeta-heterodimers,紫色光合膜的细菌。它们包含大量生色团的组织优化的光吸收和快速光能量迁移。最近,nonameric的结构的LH-2 Rhodopseudomonas acidophila已确定;我们在这里报告的晶体结构octameric LH-2从Rhodospirillum molischianum。异同的公布这些蛋白质的体系结构可以提供宝贵的见解细菌光合作用的有效的能量转移机制。结果:晶体结构的LH-2 Rs. molischianum一直由分子替换使用x射线衍射分辨率2.4。16岁的晶体结构显示两个同轴圆筒membrane-spanning螺旋单元,包含两个戒指的bacteriochlorophyll-a (BChl-a)分子。一环由16个B850 BChl-as垂直于膜面和其他八个B800 BChl-as几乎平行于膜面;八membrane-spanning蕃茄(这个复杂的主要类胡萝卜素)伸出B800和B850 BChl-as。的B800 BChl-as展览不同的结扎石头剪刀。 acidophila (aspartate is the Mg ligand as opposed to formyl-methionine in Rps. acidophila). CONCLUSIONS: The light-harvesting complexes from different bacteria assume various ring sizes. In LH-2 of Rs. molischianum, the Qy transition dipole moments of neighbouring B850 and B800 BChl-as are nearly parallel to each other, that is, they are optimally aligned for Foster exciton transfer. Dexter energy transfer between these chlorophylls is also possible through interactions mediated by lycopenes and B850 BChl-a phytyl tails; the B800 BChl-a and one of the two B850 BChl-as associated with each heterodimeric unit are in van der Waals distance to a lycopene, such that singlet and triplet energy transfer between lycopene and the BChl-as can occur by the Dexter mechanism. The ring structure of the B850 BChl-as is optimal for light energy transfer in that it samples all spatial absorption and emission characteristics and places all oscillator strength into energetically low lying, thermally accessible exciton states.