Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel.
Elife. 2017 Aug 31;6:e28034. doi: 10.7554/eLife.28034.
Growing cells coordinate protein translation with metabolic rates. Central to this coordination is ribosome production. Ribosomes drive cell growth, but translation of ribosomal proteins competes with production of non-ribosomal proteins. Theory shows that cell growth is maximized when all expressed ribosomes are constantly translating. To examine whether budding yeast function at this limit of full ribosomal usage, we profiled the proteomes of cells growing in different environments. We find that cells produce excess ribosomal proteins, amounting to a constant ≈8% of the proteome. Accordingly, ≈25% of ribosomal proteins expressed in rapidly growing cells does not contribute to translation. Further, this fraction increases as growth rate decreases and these excess ribosomal proteins are employed when translation demands unexpectedly increase. We suggest that steadily growing cells prepare for conditions that demand increased translation by producing excess ribosomes, at the expense of lower steady-state growth rate.
细胞生长通过协调蛋白质翻译与代谢率来实现。这种协调的核心是核糖体的产生。核糖体驱动细胞生长，但核糖体蛋白的翻译与非核糖体蛋白的产生存在竞争。理论表明，当所有表达的核糖体都在持续翻译时，细胞生长达到最大化。为了研究出芽酵母是否在充分利用核糖体的这一极限条件下发挥功能，我们对在不同环境中生长的细胞的蛋白质组进行了分析。我们发现，细胞产生了过量的核糖体蛋白，约占蛋白质组的恒定 8%。因此，在快速生长的细胞中表达的约 25%的核糖体蛋白不参与翻译。此外，当翻译需求意外增加时，这个比例会增加，并且这些多余的核糖体蛋白会被利用。我们认为，稳定生长的细胞通过产生多余的核糖体来为需要增加翻译的情况做准备，这会以牺牲较低的稳态生长速度为代价。
