Molecular architecture of the thylakoid membrane: Lipid diffusion space for plastoquinone
Molecular architecture of the thylakoid membrane: Lipid diffusion space for plastoquinone
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DOI：
10.1021/bi011650y
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发表时间：
2002-04-16
期刊：
影响因子：
2.9
通讯作者：
Galla, HJ
中科院分区：
文献类型：
--
作者：
Kirchhoff, H;Mukherjee, U;Galla, HJ
我们测定了菠菜类囊体膜组分(脂和蛋白质)的化学计量组成，并求出了这些组分所占的分子面积。根据这一分析，得到了脂相扩散空间、位于第一蛋白质溶剂化壳层的脂类的比例(界面脂)和质醌(PQ)浓度。在这些化学计量数据的基础上，我们分析了PQ在光系统(PS)II和细胞色素(Cyt.)根据渗流理论，这种高蛋白的BF复合体可以阻隔膜(蛋白质面积约70%)。这一分析揭示了一个低效的扩散过程。我们认为，类囊体膜的独特结构特征(颗粒形成、微区)有助于将这些低效降至最低，并确保非速率限制的P-Q扩散过程。大量已发表的证据支持这样一种观点，即存在较高的蛋白质关联性，特别是在基粒类囊体中。从边界脂分数(约60%)的定量，我们得出结论，参与这些结合的蛋白质复合体应该由脂类隔开。类囊体脂间隔的蛋白质聚集在性质上不同于以前描述的缔合(多亚单位复合体、超复合体)。我们得到了类囊体膜中蛋白质和脂类相互作用的层次结构。
We have determined the stoichiometric composition of membrane components (lipids and proteins) in spinach thylakoids and have derived the molecular area occupied by these components. From this analysis, the lipid phase diffusion space, the fraction of lipids located in the first protein solvation shell (boundary lipids), and the plastoquinone (PQ) concentration are derived. On the basis of these stoichiometric data, we have analyzed the motion of PQ between photosystem (PS) II and cytochrome (cyt.) bf complexes in this highly protein obstructed membrane (protein area about 70%) using percolation theory. This analysis reveals an inefficient diffusion process. We propose that distinct structural features of the thylakoid membrane (grana formation, microdomains) could help to minimize these inefficiencies and ensure a non-rate limiting P Q diffusion process. A large amount of published evidence supports the idea that higher protein associations exist, especially in grana thylakoids. From the quantification of the boundary lipid fraction (about 60%), we conclude that protein complexes involved in these associations should be spaced by lipids. Lipid-spaced protein aggregations in thylakoids are qualitatively different to previously characterized associations (multisubunit complexes, supercomplexes). We derive a hierarchy of protein and lipid interactions in the thylakoid membrane.