Nishimura Kenji, Apitz Janina, Friso Giulia, Kim Jitae, Ponnala Lalit, Grimm Bernhard, van Wijk Klaas J
Department of Plant Biology, Cornell University, Ithaca, New York 14853.
Department of Plant Physiology, Humboldt University, 10115 Berlin, Germany.
Plant Cell. 2015 Oct;27(10):2677-91. doi: 10.1105/tpc.15.00574. Epub 2015 Sep 29.
Clp proteases are found in prokaryotes, mitochondria, and plastids where they play crucial roles in maintaining protein homeostasis (proteostasis). The plant plastid Clp machinery comprises a hetero-oligomeric ClpPRT proteolytic core, ATP-dependent chaperones ClpC and ClpD, and an adaptor protein, ClpS1. ClpS1 selects substrates to the ClpPR protease-ClpC chaperone complex for degradation, but the underlying substrate recognition and delivery mechanisms are currently unclear. Here, we characterize a ClpS1-interacting protein in Arabidopsis thaliana, ClpF, which can interact with the Clp substrate glutamyl-tRNA reductase. ClpF and ClpS1 mutually stimulate their association with ClpC. ClpF, which is only found in photosynthetic eukaryotes, contains bacterial uvrB/C and YccV protein domains and a unique N-terminal domain. We propose a testable model in which ClpS1 and ClpF form a binary adaptor for selective substrate recognition and delivery to ClpC, reflecting an evolutionary adaptation of the Clp system to the plastid proteome.
Clp蛋白酶存在于原核生物、线粒体和质体中，它们在维持蛋白质稳态（蛋白质动态平衡）方面发挥着关键作用。植物质体Clp机制包括一个异源寡聚的ClpPRT蛋白水解核心、ATP依赖的伴侣蛋白ClpC和ClpD，以及一个衔接蛋白ClpS1。ClpS1将底物选择到ClpPR蛋白酶-ClpC伴侣蛋白复合物进行降解，但目前尚不清楚潜在的底物识别和传递机制。在这里，我们鉴定了拟南芥中一种与ClpS1相互作用的蛋白ClpF，它可以与Clp底物谷氨酰胺-tRNA还原酶相互作用。ClpF和ClpS1相互刺激它们与ClpC的结合。仅在光合真核生物中发现的ClpF包含细菌uvrB/C和YccV蛋白结构域以及一个独特的N端结构域。我们提出了一个可验证的模型，其中ClpS1和ClpF形成一个二元衔接子，用于选择性底物识别并传递给ClpC，这反映了Clp系统对质体蛋白质组的进化适应。
