Reversible particle movements associated with unstacking and restacking of chloroplast membranes in vitro.
Reversible particle movements associated with unstacking and restacking of chloroplast membranes in vitro.
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DOI：
10.1083/jcb.71.1.136
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发表时间：
1976-10
影响因子：
7.8
通讯作者：
Staehelin, L A
中科院分区：
文献类型：
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作者：
Staehelin, L A
冷冻断裂和冷冻蚀刻技术已被用来研究离体菠菜叶绿体膜的超分子结构，并监测与这些膜在体外unstacking和restacking的结构变化。从正常叶绿体膜的四个断裂面制备的高分辨率颗粒大小直方图揭示了存在四种不同类别的非随机分布在基粒和基质膜之间的膜内颗粒。大表面颗粒与EF-面颗粒表现出一一对应的关系。由于这些颗粒之间的基粒和基质膜的分布相吻合的光系统II（PS II）的活动的分布，有人认为，它们可能是PS II复合物的结构等价物。描述所有类别的颗粒之间的结构关系的解释模型。在低盐培养基中至少45分钟的叶绿体膜的实验性解堆导致lamelae的重组，并通过膜平面中的平移运动导致不同类别的膜颗粒的伴随混合。通过向膜悬浮液中加入2-20 mM MgCl 2或100-200 mM NaCl，可以实现这种实验上未堆叠的叶绿体膜的体外重新堆叠。允许在室温下重新堆叠至少1小时的膜证明EF面颗粒重新聚集到新形成的堆叠膜区域中，以产生与正常堆叠对照几乎不可区分的图案和尺寸分布。重新堆叠发生在两个步骤：一个快速粘附相邻的基质膜表面几乎没有颗粒运动，和一个更慢的扩散额外的大的膜内颗粒进入堆叠的区域，在那里他们成为被困。叶绿素a：叶绿素B的比率从正常的，未堆叠的，和重新堆叠的膜获得的膜部分表明，粒子的运动是由色素分子的运动。定向和可逆运动的膜颗粒在孤立的叶绿体相比，那些报道的质膜颗粒。
Freeze-fracture and freeze-etch techniques have been employed to study the supramolecular structure of isolated spinach chloroplast membranes and to monitor structural changes associated with in vitro unstacking and restacking of these membranes. High-resolution particle size histograms prepared from the four fracture faces of normal chloroplast membranes reveal the presence of four distinct categories of intramembranous particles that are nonrandomly distributed between grana and stroma membranes. The large surface particles show a one to one relationship with the EF-face particles. Since the distribution of these particles between grana and stroma membranes coincides with the distribution of photosystem II (PS II) activity, it is argued that they could be structural equivalents of PS II complexes. An interpretative model depicting the structural relationship between all categories of particles is presented. Experimental unstacking of chloroplast membranes in low-salt medium for at least 45 min leads to a reorganization of the lamellae and to a concomitant intermixing of the different categories of membrane particles by means of translational movements in the plane of the membrane. In vitro restacking of such experimentally unstacked chloroplast membranes can be achieved by adding 2-20 mM MgCl2 or 100-200 mM NaCl to the membrane suspension. Membranes allowed to restack for at least 1 h at room temperature demonstrate a resegregation of the EF-face particles into the newly formed stacked membrane regions to yield a pattern and a size distribution nearly indistinguishable from the normally stacked controls. Restacking occurs in two steps: a rapid adhesion of adjoining stromal membrane surfaces with little particle movement, and a slower diffusion of additional large intramembranous particles into the stacked regions where they become trapped. Chlorophyll a:chlorophyll b ratios of membrane fraction obtained from normal, unstacked, and restacked membranes show that the particle movements are paralleled by movements of pigment molecules. The directed and reversible movements of membrane particles in isolated chloroplasts are compared with those reported for particles of plasma membranes.