Baumgartel D M, Howell S H
Biochemistry. 1977 Jul 12;16(14):3182-9. doi: 10.1021/bi00633a022.
Changes in the rate of protein synthesis during the cell cycle of Chlamydomonas reinhardi have been measured by determining changes in the separate rates of polypeptide chain initiation and elongation and in the rate of incorporation of a radioactive amino acid. The rate of polypeptide chain elongation, determined from the relative rates of labeling of two size classes of polyribosomes, varies only about twofold during the cell cycle. The rate of polypeptide chain initiation, determined from an analysis of the distribution of ribosomes in monoribosomes (and ribosomal subunits) and polyribosomes, varies more than 25-fold. Also, the overall rate of protein synthesis during the cell cycle varies to the same extent as the rate of chain initiation. Measurement of protein synthetic rates using incorporation of a radioactive amino acid ([3H]arginine) underestimates the actual change in the rate of protein synthesis during the cell cycle. The vast changes in the initiation rate during the cell cycle suggest a mechanism for selecting specific messenger RNAs for translation at different cell-cycle stages.
通过测定多肽链起始和延伸的各自速率变化以及放射性氨基酸掺入速率的变化，已对莱茵衣藻细胞周期中蛋白质合成速率的变化进行了测量。根据两类大小不同的多核糖体的相对标记速率确定的多肽链延伸速率，在细胞周期中仅变化约两倍。根据对单核糖体（和核糖体亚基）及多核糖体中核糖体分布的分析确定的多肽链起始速率，变化超过25倍。此外，细胞周期中蛋白质合成的总体速率变化程度与链起始速率相同。使用放射性氨基酸（[³H]精氨酸）掺入来测量蛋白质合成速率会低估细胞周期中蛋白质合成速率的实际变化。细胞周期中起始速率的巨大变化提示了一种在不同细胞周期阶段选择特定信使RNA进行翻译的机制。
