Laboratory of Chemical Biodynamics, University of California, Berkeley, California 94720.
Plant Physiol. 1985 Aug;78(4):807-11. doi: 10.1104/pp.78.4.807.
Polyadenylated RNA was isolated from maize leaves and translated in vitro. In agreement with a previous report by others, we found among the translation products a 110-kilodalton pyruvate orthophosphate dikinase (PPDK) precursor that is about 16 kilodaltons larger than the polypeptide isolated from cells. This maize PPDK precursor polypeptide was taken up from the translation product mixture by intact spinach chloroplasts and yielded a mature PPDK polypeptide (94 kilodaltons). The uptake and processing support the proposal that the extra 16-kilodalton size of the polypeptide from in vitro translation of maize leaf mRNA represents a transit sequence which is cleaved after its entry into chloroplasts. Moreover, these results provide additional evidence that in vivo in maize leaf cells PPDK polypeptide is synthesized in the cytoplasm and is transported into the chloroplasts.Location of PPDK in C(3) plant leaves was investigated by immunochemical analysis. Intact chloroplasts were isolated from leaves of spinach, wheat, and maize. A protein blot of stromal protein in each case gave rise to bands corresponding to authentic PPDK polypeptide. This result indicates that PPDK is present in chloroplasts of C(3) plant leaves as it is in the case of C(4) plants.
多聚腺苷酸 RNA 从玉米叶片中分离出来，并在体外进行翻译。与其他人之前的报告一致，我们在翻译产物中发现了一种 110 千道尔顿的丙酮酸 orthophosphate dikinase（PPDK）前体，比从细胞中分离出来的多肽大约大 16 千道尔顿。这种玉米 PPDK 前体多肽被完整的菠菜叶绿体从翻译产物混合物中摄取，并产生成熟的 PPDK 多肽（94 千道尔顿）。摄取和加工支持这样的假设，即体外翻译玉米叶片 mRNA 产生的多肽额外的 16 千道尔顿大小代表一个穿梭序列，在进入叶绿体后被切割。此外，这些结果提供了额外的证据，即在活体玉米叶片细胞中，PPDK 多肽在细胞质中合成，并被运输到叶绿体中。通过免疫化学分析研究了 PPDK 在 C（3）植物叶片中的位置。从菠菜、小麦和玉米叶片中分离出完整的叶绿体。每种情况下基质蛋白的蛋白质印迹都会产生与真实 PPDK 多肽相对应的条带。这一结果表明，PPDK 存在于 C（3）植物叶片的叶绿体中，就像 C（4）植物一样。
