PDF(Pubmed)
Abstract：
We asked what peptide features govern targeting to the mitochondria versus the chloroplast, using antimicrobial peptides as a starting point. This approach was inspired by the endosymbiotic hypothesis that organelle-targeting peptides derive from antimicrobial amphipathic peptides delivered by the host cell, to which organelle progenitors became resistant. To explore the molecular changes required to convert antimicrobial into targeting peptides, we expressed a set of 13 antimicrobial peptides in Chlamydomonas reinhardtii. Peptides were systematically modified to test distinctive features of mitochondrion- and chloroplast-targeting peptides, and we assessed their targeting potential by following the intracellular localization and maturation of a Venus fluorescent reporter used as a cargo protein. Mitochondrial targeting can be achieved by some unmodified antimicrobial peptide sequences. Targeting to both organelles is improved by replacing lysines with arginines. Chloroplast targeting is enabled by the presence of flanking unstructured sequences, additional constraints consistent with chloroplast endosymbiosis having occurred in a cell that already contained mitochondria. If indeed targeting peptides evolved from antimicrobial peptides, then required modifications imply a temporal evolutionary scenario with an early exchange of cationic residues and a late acquisition of chloroplast-specific motifs.
摘要：
使用抗微生物肽作为起点，我们询问了哪些肽特征控制线粒体与叶绿体的靶向。这种方法受到内共生假说的启发，即细胞器靶向肽来自宿主细胞递送的抗微生物两亲性肽，细胞器祖细胞对其产生了抗性。为了探索将抗菌剂转化为靶向肽所需的分子变化，我们在莱茵衣藻中表达了一组13种抗菌肽。肽被系统地修饰以测试线粒体和叶绿体靶向肽的独特特征，我们通过追踪用作货物蛋白的金星荧光报道分子的细胞内定位和成熟来评估它们的靶向潜力。线粒体靶向可以通过一些未修饰的抗微生物肽序列来实现。通过用精氨酸代替赖氨酸来改善对两个细胞器的靶向。叶绿体靶向是通过侧翼非结构化序列的存在而实现的，在已经含有线粒体的细胞中发生了与叶绿体内共生一致的其他约束。如果靶向肽确实是从抗菌肽进化而来的，所需的修改意味着阳离子残基早期交换的时间进化情景，和叶绿体特定基序的晚期获得。
