Adam Z, Ostersetzer O
Institute of Plant Sciences, The Hebrew University, Rehovot 76100, Israel.
Biochem Soc Trans. 2001 Aug;29(Pt 4):427-30. doi: 10.1042/bst0290427.
To study protein degradation in thylakoid membranes we identified, characterized and cloned thylakoid proteases, and then linked them to known proteolytic processes. Several families of chloroplast proteases were identified and characterized to different extents. FtsH, an ATP-dependent metalloprotease that belongs to the AAA-protein family, was found to be integral to the thylakoid membrane, facing the stroma. It is involved in both the degradation of unassembled subunits of membrane complexes, such as the Rieske Fe-S protein of the cytochrome complex, and the degradation of oxidatively damaged proteins such as the D1 protein of the photosystem II (PS II) reaction centre. Plant genomes contain multiple isomers of this protease but the functional significance of this multiplication is not clear yet. A second protease, the serine ATP-independent DegP, was found to be strongly associated with the luminal side of the thylakoid membrane. Although a specific role has not yet assigned for it, its location suggests that it can degrade luminal soluble proteins as well as luminally exposed regions of thylakoid membrane proteins.
为了研究类囊体膜中的蛋白质降解，我们鉴定、表征并克隆了类囊体蛋白酶，然后将它们与已知的蛋白水解过程联系起来。已鉴定出几个叶绿体蛋白酶家族，并对其进行了不同程度的表征。FtsH是一种属于AAA蛋白家族的ATP依赖性金属蛋白酶，被发现是类囊体膜的组成部分，面向基质。它既参与膜复合物未组装亚基的降解，如细胞色素复合物的 Rieske Fe-S 蛋白，也参与氧化损伤蛋白的降解，如光系统 II（PS II）反应中心的 D1 蛋白。植物基因组包含这种蛋白酶的多个异构体，但这种倍增的功能意义尚不清楚。第二种蛋白酶，即不依赖ATP的丝氨酸蛋白酶DegP，被发现与类囊体膜的腔面紧密相关。尽管尚未确定其具体作用，但其位置表明它可以降解腔面可溶性蛋白以及类囊体膜蛋白的腔面暴露区域。
