Yoshida Biological Laboratory, 11-1, Takehanasotoda-cho, Yamashina-ku, Kyoto 607-8081, Japan.
Genes Cells. 2010 Jan;15(1):43-58. doi: 10.1111/j.1365-2443.2009.01364.x. Epub 2009 Dec 15.
In the stationary growth phase of Escherichia coli, the 70S ribosomes are dimerized by the ribosome modulation factor (RMF) and hibernation promoting factor (HPF) proteins to form 100S ribosomes, which lose translational activity. In this study we found 100S ribosomes in the gram-positive bacterium Staphylococcus aureus, which has an HPF homolog (named SaHPF) but no RMF homolog. Unlike in E. coli, 100S ribosomes exist in all growth phases of S. aureus, with the highest levels at the transition from the exponential phase to the stationary phase. To find the key factors involved in 100S formation, we analyzed proteins associated with crude ribosomes using radical-free and highly reducing 2-D PAGE and MALDI TOF/MS. Only the SaHPF levels changed in parallel with the changes in 100S levels. SaHPF bound preferentially to 70S components in 100S ribosomes, with a molar ratio of 1 : 1 relative to the 70S, but some SaHPF was also detected in free 70S ribosomes. High-salt washing of the crude ribosomes released SaHPF and dissociated the 100S ribosomes to their 70S components. When these 70S components were incubated with purified SaHPF in vitro, they re-associated to form 100S. These results suggest that SaHPF is a key protein involved in 100S ribosome formation in S. aureus.
在大肠杆菌的静止生长阶段，70S 核糖体通过核糖体调节因子（RMF）和休眠促进因子（HPF）蛋白二聚化形成 100S 核糖体，从而失去翻译活性。在这项研究中，我们在革兰氏阳性菌金黄色葡萄球菌中发现了 100S 核糖体，它有一个 HPF 同源物（命名为 SaHPF），但没有 RMF 同源物。与大肠杆菌不同，100S 核糖体存在于金黄色葡萄球菌的所有生长阶段，在从指数期到静止期的过渡阶段水平最高。为了找到参与 100S 形成的关键因素，我们使用无自由基和高度还原的 2-D PAGE 和 MALDI TOF/MS 分析了与粗核糖体相关的蛋白质。只有 SaHPF 的水平与 100S 水平的变化平行变化。SaHPF 优先与 100S 核糖体中的 70S 成分结合，与 70S 的摩尔比为 1 : 1，但也在游离 70S 核糖体中检测到一些 SaHPF。粗核糖体的高盐洗涤释放 SaHPF 并将 100S 核糖体解离为其 70S 成分。当这些 70S 成分在体外与纯化的 SaHPF 孵育时，它们重新结合形成 100S。这些结果表明，SaHPF 是金黄色葡萄球菌 100S 核糖体形成的关键蛋白。
