Law Yee-Song, Zhang Renshan, Guan Xiaoqian, Cheng Shifeng, Sun Feng, Duncan Owen, Murcha Monika W, Whelan James, Lim Boon Leong
School of Biological Sciences, University of Hong Kong, Pokfulam, Hong Kong, China (Y.-S.L., R.Z., X.G., S.C., F.S., B.L.L.);Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley, Western Australia 6009, Australia (O.D., M.W.M.);Department of Animal, Plant, and Soil Science, School of Life Science, Australian Research Council Centre of Excellence in Plant Energy Biology, La Trobe University, Bundoora, Victoria 3086, Australia (J.W.); andState Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, Hong Kong, China (B.L.L.).
School of Biological Sciences, University of Hong Kong, Pokfulam, Hong Kong, China (Y.-S.L., R.Z., X.G., S.C., F.S., B.L.L.);Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley, Western Australia 6009, Australia (O.D., M.W.M.);Department of Animal, Plant, and Soil Science, School of Life Science, Australian Research Council Centre of Excellence in Plant Energy Biology, La Trobe University, Bundoora, Victoria 3086, Australia (J.W.); andState Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, Hong Kong, China (B.L.L.)
Plant Physiol. 2015 Oct;169(2):1344-55. doi: 10.1104/pp.15.01115. Epub 2015 Aug 24.
The nucleus-encoded mitochondria-targeted proteins, multiple organellar RNA editing factors (MORF3, MORF5, and MORF6), interact with Arabidopsis (Arabidopsis thaliana) PURPLE ACID PHOSPHATASE2 (AtPAP2) located on the chloroplast and mitochondrial outer membranes in a presequence-dependent manner. Phosphorylation of the presequence of the precursor MORF3 (pMORF3) by endogenous kinases in wheat germ translation lysate, leaf extracts, or STY kinases, but not in rabbit reticulocyte translation lysate, resulted in the inhibition of protein import into mitochondria. This inhibition of import could be overcome by altering threonine/serine residues to alanine on the presequence, thus preventing phosphorylation. Phosphorylated pMORF3, but not the phosphorylation-deficient pMORF3, can form a complex with 14-3-3 proteins and HEAT SHOCK PROTEIN70. The phosphorylation-deficient mutant of pMORF3 also displayed faster rates of import when translated in wheat germ lysates. Mitochondria isolated from plants with altered amounts of AtPAP2 displayed altered protein import kinetics. The import rate of pMORF3 synthesized in wheat germ translation lysate into pap2 mitochondria was slower than that into wild-type mitochondria, and this rate disparity was not seen for pMORF3 synthesized in rabbit reticulocyte translation lysate, the latter translation lysate largely deficient in kinase activity. Taken together, these results support a role for the phosphorylation and dephosphorylation of pMORF3 during the import into plant mitochondria. These results suggest that kinases, possibly STY kinases, and AtPAP2 are involved in the import of protein into both mitochondria and chloroplasts and provide a mechanism by which the import of proteins into both organelles may be coordinated.
细胞核编码的线粒体靶向蛋白,即多种细胞器RNA编辑因子(MORF3、MORF5和MORF6),以前序列依赖的方式与位于叶绿体和线粒体外膜上的拟南芥紫色酸性磷酸酶2(AtPAP2)相互作用。小麦胚翻译裂解物、叶片提取物或STY激酶中的内源性激酶可使前体MORF3(pMORF3)的前序列发生磷酸化,但兔网织红细胞翻译裂解物中不会,这种磷酸化导致蛋白质向线粒体的导入受到抑制。通过将前序列上的苏氨酸/丝氨酸残基替换为丙氨酸来防止磷酸化,可克服这种导入抑制。磷酸化的pMORF3而非磷酸化缺陷型的pMORF3能与14-3-3蛋白和热休克蛋白70形成复合物。pMORF3的磷酸化缺陷型突变体在小麦胚裂解物中翻译时也表现出更快的导入速率。从AtPAP2含量改变的植物中分离出的线粒体显示出改变的蛋白质导入动力学。在小麦胚翻译裂解物中合成的pMORF3导入pap2线粒体的速率比导入野生型线粒体的速率慢,而在兔网织红细胞翻译裂解物中合成的pMORF3则未观察到这种速率差异,后者翻译裂解物中激酶活性基本缺失。综上所述,这些结果支持pMORF3在导入植物线粒体过程中磷酸化和去磷酸化的作用。这些结果表明,激酶(可能是STY激酶)和AtPAP2参与蛋白质向线粒体和叶绿体的导入,并提供了一种协调蛋白质向这两种细胞器导入的机制。