Sasaki Y, Tomoda Y, Tomi H, Kamikubo T, Shinozaki K
Eur J Biochem. 1985 Oct 1;152(1):179-86. doi: 10.1111/j.1432-1033.1985.tb09179.x.
Ribulose biphosphate carboxylase/oxygenase, with its large subunit encoded in the chloroplast and the small subunit in the nucleus, is induced by light. Accumulation of the enzyme, its two mRNA levels, and the synthesis rate of enzyme protein in pea leaves were followed during induction to understand the role of mRNA levels during greening subunit synthesis. The relative mRNA levels for the large and the small subunits increased coordinately up to 3-4 days, which almost corresponded to an inflection point of the accumulation profile of RuBisCO, and then the two mRNA levels gradually decreased. To obtain information of subunit synthesis, the extent of labelling of the two subunits were determined for both assembled and unassembled subunits using specific IgG. Unassembled subunits were found for both polypeptides, with a slight excess of the small one. The observed synthesis rates of the small and the large subunits were roughly coordinated without overproduction and almost stoichiometric amounts of the two polypeptides were found. The profiles of observed synthesis rate of the two subunits and the holoenzyme were similar to those of their mRNA levels. These results suggest that the synthesis of ribulose biphosphate carboxylase/oxygenase protein and its accumulation are dependent on the coordinated change of the two mRNA levels in greening pea leaves.
1,5 - 二磷酸核酮糖羧化酶/加氧酶，其大亚基由叶绿体编码，小亚基由细胞核编码，受光诱导。在诱导过程中跟踪豌豆叶片中该酶的积累、其两种mRNA水平以及酶蛋白的合成速率，以了解mRNA水平在绿化亚基合成过程中的作用。大亚基和小亚基的相对mRNA水平在3 - 4天内协同增加，这几乎与RuBisCO积累曲线的拐点相对应，然后两种mRNA水平逐渐下降。为了获得亚基合成的信息，使用特异性IgG测定了组装和未组装亚基中两种亚基的标记程度。发现两种多肽都有未组装的亚基，小亚基略有过量。观察到的小亚基和大亚基的合成速率大致协调，没有过量产生，并且发现两种多肽的量几乎是化学计量的。观察到的两种亚基和全酶的合成速率曲线与其mRNA水平的曲线相似。这些结果表明，1,5 - 二磷酸核酮糖羧化酶/加氧酶蛋白的合成及其积累依赖于绿化豌豆叶片中两种mRNA水平的协同变化。
