Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 33101, USA.
Mol Cell. 2011 Oct 7;44(1):160-6. doi: 10.1016/j.molcel.2011.06.037.
RNase R, an Escherichia coli exoribonuclease important for degradation of structured RNAs, increases 3- to 10-fold under certain stress conditions, due to an increased half-life for this usually unstable protein. Components of the trans-translation machinery, tmRNA, and its associated protein, SmpB, are essential for RNase R instability. However, it is not understood why exponential phase RNase R is unstable or how it becomes stabilized in stationary phase. Here, we show that these phenomena are regulated by acetylation catalyzed by YfiQ protein. One residue, Lys544, is acetylated in exponential phase RNase R, but not in the stationary phase protein, resulting in tighter binding of tmRNA-SmpB to the C-terminal region of exponential phase RNase R and subsequent proteolytic degradation. Removal of the positive charge at Lys544 or a negative charge in the C-terminal region likely disrupts their interaction, facilitating tmRNA-SmpB binding. These findings indicate that acetylation can regulate the stability of a bacterial protein.
RNase R 是一种大肠杆菌的外切核酸酶，对于结构 RNA 的降解至关重要。在某些应激条件下，由于这种通常不稳定的蛋白质半衰期延长，RNase R 的含量增加了 3 到 10 倍。转译转译机制的组件、tmRNA 及其相关蛋白 SmpB，对于 RNase R 的不稳定性是必不可少的。然而，目前尚不清楚为什么指数期 RNase R 不稳定，以及它如何在静止期变得稳定。在这里，我们表明这些现象是由 YfiQ 蛋白催化的乙酰化作用调节的。一个残基，Lys544，在指数期的 RNase R 中被乙酰化，但在静止期的蛋白质中没有，导致 tmRNA-SmpB 与指数期 RNase R 的 C 末端区域结合更紧密，随后发生蛋白水解降解。赖氨酸 544 上的正电荷或 C 末端区域的负电荷的去除可能破坏了它们的相互作用，从而促进了 tmRNA-SmpB 的结合。这些发现表明，乙酰化可以调节细菌蛋白的稳定性。
