Firlej-Kwoka Ewa, Strittmatter Penelope, Soll Jürgen, Bölter Bettina
Department Biology I, Plant Biochemistry, Ludwig-Maximilians-Universität München, Grosshadernerstr. 2-4, 82152 Planegg-Martinsried, Germany.
Plant Mol Biol. 2008 Nov;68(4-5):505-19. doi: 10.1007/s11103-008-9387-4. Epub 2008 Aug 14.
The chloroplast inner envelope membrane contains many integral proteins which differ in the number of alpha-helices that anchor the protein into the bilayer. For most of these proteins it is not known which pathway they engage to reach their final localisation within the membrane. In yeast mitochondria, two distinct sorting/insertion pathways have been described for integral inner membrane proteins, involving the Tim22 and Tim23 translocases. These routes involve on the one hand a conservative sorting, on the other hand a stop-transfer pathway. In this study we performed a systematic characterisation of the import behaviour of seven inner envelope proteins representing different numbers of predicted alpha-helices. We investigated their energy dependence, import rate, involvement of components of the chloroplast general import pathway and distribution between soluble and membrane fractions. Our results show the existence of at least two different families of inner envelope proteins that can be classified due to the occurrence of an intermediate processing form. Each of the proteins we investigated seems to use a stop-transfer pathway for insertion into the inner envelope.
叶绿体内膜含有许多整合蛋白，这些蛋白锚定到双层膜中的α-螺旋数量各不相同。对于这些蛋白中的大多数而言，它们通过何种途径到达膜内的最终定位尚不清楚。在酵母线粒体中，已描述了内膜整合蛋白的两种不同的分选/插入途径，涉及Tim22和Tim23转位酶。这些途径一方面涉及保守分选，另一方面涉及停止转移途径。在本研究中，我们对代表不同预测α-螺旋数量的七种内膜蛋白的导入行为进行了系统表征。我们研究了它们对能量的依赖性、导入速率、叶绿体一般导入途径各组分的参与情况以及在可溶性和膜组分之间的分布。我们的结果表明，至少存在两个不同的内膜蛋白家族，可根据中间加工形式的出现进行分类。我们研究的每种蛋白似乎都使用停止转移途径插入内膜。
