Sasaki Y, Kozaki A, Ohmori A, Iguchi H, Nagano Y
Laboratory of Plant Molecular Biology, Graduate School of Agricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
J Biol Chem. 2001 Feb 9;276(6):3937-40. doi: 10.1074/jbc.M008166200. Epub 2000 Nov 14.
RNA editing is an important post-transcriptional process in chloroplasts and is thought to be functionally significant. Here we show a requirement of RNA editing for a functional enzyme. In peas, acetyl-CoA carboxylase (ACCase), a key enzyme of fatty acid synthesis, is composed of biotin carboxylase with the biotin carboxyl carrier protein and carboxyltransferase (CT). CT is composed of the nuclear-encoded alpha polypeptide and the chloroplast-encoded beta polypeptide in peas. One nucleotide of the beta polypeptide mRNA, which is edited in pea chloroplasts, converts the serine codon to the leucine codon. We show that this RNA editing is required for functional CT by comparing the unedited and edited recombinant enzymes. In plants not having a leucine codon at the same position, editing was shown to take place so as to create the leucine codon, indicating that editing is needed for in vivo CT activity and therefore for ACCase. To our knowledge, ACCase is an essential enzyme, suggesting that the chloroplast RNA editing is necessary for these plants.
RNA编辑是叶绿体中一种重要的转录后过程，被认为具有重要的功能意义。在此我们展示了功能性酶对RNA编辑的需求。在豌豆中，脂肪酸合成的关键酶乙酰辅酶A羧化酶（ACCase）由生物素羧化酶与生物素羧基载体蛋白以及羧基转移酶（CT）组成。在豌豆中，CT由核编码的α多肽和叶绿体编码的β多肽组成。β多肽mRNA的一个核苷酸在豌豆叶绿体中被编辑，将丝氨酸密码子转换为亮氨酸密码子。通过比较未编辑和编辑后的重组酶，我们表明这种RNA编辑是功能性CT所必需的。在相同位置没有亮氨酸密码子的植物中，显示会发生编辑以产生亮氨酸密码子，这表明编辑对于体内CT活性以及因此对于ACCase是必需的。据我们所知，ACCase是一种必需酶，这表明叶绿体RNA编辑对于这些植物是必要的。
