Arrangement of Photosystem II and ATP Synthase in Chloroplast Membranes of Spinach and Pea
Arrangement of Photosystem II and ATP Synthase in Chloroplast Membranes of Spinach and Pea
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DOI：
10.1105/tpc.109.071431
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发表时间：
2010-04-01
期刊：
影响因子：
11.6
通讯作者：
Kuehlbrandt, Werner
中科院分区：
文献类型：
--
作者：
Daum, Bertram;Nicastro, Daniela;Kuehlbrandt, Werner
我们用冷冻电子断层扫描揭示的安排光系统II（PSII）和ATP合酶在玻璃体部分的完整的叶绿体和暴跌冷冻悬浮液分离的类囊体膜。我们发现基质和基粒类囊体在基粒边缘通过交错的片状膜突起连接。在冷冻水合的叶绿体中的基粒膜的堆叠重复是15.7 nm，具有4.5 nm的内腔空间和平坦的基质表面之间的3.2 nm的距离。叶绿体ATP合酶被限制在基粒端膜和基质层的最小弯曲区域，在那里它覆盖20%的表面积。总的来说，85%的ATP酶是单体，其余的形成两个或更多个拷贝的随机组装体。PSII和捕光复合物II（LHCII）的超复合物偶尔会形成有序的阵列在贴伏基粒类囊体，而这种秩序是失去了去堆积膜。在有序阵列中，基质间隙两侧的每个膜都包含超复合物的二维晶体，两个晶格排列使得PSII核心，LHCII三聚体和次要LHC各自面对相对膜中相同类型的复合物。基粒的形成可能是由于这些复合物之间的静电相互作用跨越基质间隙。
We used cryoelectron tomography to reveal the arrangements of photosystem II (PSII) and ATP synthase in vitreous sections of intact chloroplasts and plunge-frozen suspensions of isolated thylakoid membranes. We found that stroma and grana thylakoids are connected at the grana margins by staggered lamellar membrane protrusions. The stacking repeat of grana membranes in frozen-hydrated chloroplasts is 15.7 nm, with a 4.5-nm lumenal space and a 3.2-nm distance between the flat stromal surfaces. The chloroplast ATP synthase is confined to minimally curved regions at the grana end membranes and stroma lamellae, where it covers 20% of the surface area. In total, 85% of the ATP synthases are monomers and the remainder form random assemblies of two or more copies. Supercomplexes of PSII and light-harvesting complex II (LHCII) occasionally form ordered arrays in appressed grana thylakoids, whereas this order is lost in destacked membranes. In the ordered arrays, each membrane on either side of the stromal gap contains a two-dimensional crystal of supercomplexes, with the two lattices arranged such that PSII cores, LHCII trimers, and minor LHCs each face a complex of the same kind in the opposite membrane. Grana formation is likely to result from electrostatic interactions between these complexes across the stromal gap.