Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan.
Biodiversity Division, National Institute for Environmental Studies, Ibaraki 305-8506, Japan.
J Cell Sci. 2024 Jul 15;137(14). doi: 10.1242/jcs.262042. Epub 2024 Jul 23.
Mitochondrial biogenesis relies on hundreds of proteins that are derived from genes encoded in the nucleus. According to the characteristic properties of N-terminal targeting peptides (TPs) and multi-step authentication by the protein translocase called the TOM complex, nascent polypeptides satisfying the requirements are imported into mitochondria. However, it is unknown whether eukaryotic cells with a single mitochondrion per cell have a similar complexity of presequence requirements for mitochondrial protein import compared to other eukaryotes with multiple mitochondria. Based on putative mitochondrial TP sequences in the unicellular red alga Cyanidioschyzon merolae, we designed synthetic TPs and showed that functional TPs must have at least one basic residue and a specific amino acid composition, although their physicochemical properties are not strictly determined. Combined with the simple composition of the TOM complex in C. merolae, our results suggest that a regional positive charge in TPs is verified solely by TOM22 for mitochondrial protein import in C. merolae. The simple authentication mechanism indicates that the monomitochondrial C. merolae does not need to increase the cryptographic complexity of the lock-and-key mechanism for mitochondrial protein import.
线粒体生物发生依赖于数百种蛋白质，这些蛋白质来源于细胞核编码的基因。根据 N 端靶向肽 (TP) 的特征性质和称为 TOM 复合物的蛋白质易位酶的多步验证，满足要求的新生多肽被导入线粒体。然而，对于每个细胞只有一个线粒体的真核细胞，与具有多个线粒体的其他真核生物相比，其线粒体蛋白输入是否具有类似的前导序列要求的复杂性尚不清楚。基于单细胞红藻 Cyanidioschyzon merolae 中的假定线粒体 TP 序列，我们设计了合成 TP，并表明功能 TP 必须至少具有一个碱性残基和特定的氨基酸组成，尽管它们的理化性质并非严格确定。结合 C. merolae 中 TOM 复合物的简单组成，我们的结果表明，TP 中的局部正电荷仅由 TOM22 验证，用于 C. merolae 中的线粒体蛋白输入。简单的验证机制表明，单核线粒体 C. merolae 不需要增加线粒体蛋白输入的锁钥机制的密码复杂性。
