Department of Physics, University of Alberta, Edmonton, Alberta, Canada.
PLoS One. 2011;6(11):e27651. doi: 10.1371/journal.pone.0027651. Epub 2011 Nov 16.
The protein p53 plays an active role in the regulation of cell cycle. In about half of human cancers, the protein is inactivated by mutations located primarily in its DNA-binding domain. Interestingly, a number of these mutations possess temperature-induced DNA-binding characteristics. A striking example is the mutation of Arg248 into glutamine or tryptophan. These mutants are defective for binding to DNA at 310 K although they have been shown to bind specifically to several p53 response elements at sub-physiological temperatures (298-306 K).
METHODOLOGY/PRINCIPAL FINDINGS: This important experimental finding motivated us to examine the effects of temperature on the structure and configuration of R248Q mutant and compare it to the wild type protein. Our aim is to determine how and where structural changes of mutant variants take place due to temperature changes. To answer these questions, we compared the mutant to the wild-type proteins from two different aspects. First, we investigated the systems at the atomistic level through their DNA-binding affinity, hydrogen bond networks and spatial distribution of water molecules. Next, we assessed changes in their long-lived conformational motions at the coarse-grained level through the collective dynamics of their side-chain and backbone atoms separately.
The experimentally observed effect of temperature on the DNA-binding properties of p53 is reproduced. Analysis of atomistic and coarse-grained data reveal that changes in binding are determined by a few key residues and provide a rationale for the mutant-loss of binding at physiological temperatures. The findings can potentially enable a rescue strategy for the mutant structure.
蛋白质 p53 在细胞周期的调节中起着积极的作用。在大约一半的人类癌症中，蛋白质由于主要位于其 DNA 结合域的突变而失活。有趣的是，许多这些突变具有温度诱导的 DNA 结合特性。一个引人注目的例子是 Arg248 突变为谷氨酰胺或色氨酸。这些突变体在 310 K 时不能结合 DNA，尽管它们已经被证明可以在低于生理温度（298-306 K）下特异性结合几个 p53 反应元件。
方法/主要发现：这一重要的实验发现促使我们研究温度对 R248Q 突变体结构和构型的影响，并将其与野生型蛋白进行比较。我们的目的是确定由于温度变化，突变变体的结构变化是如何以及在何处发生的。为了回答这些问题，我们从两个不同的方面将突变体与野生型蛋白进行了比较。首先，我们通过 DNA 结合亲和力、氢键网络和水分子的空间分布，在原子水平上研究了这些系统。接下来，我们通过侧链和主链原子的集体动力学，在粗粒化水平上评估了它们的长寿命构象运动的变化。
实验观察到的温度对 p53 的 DNA 结合特性的影响得到了重现。原子和粗粒化数据的分析表明，结合的变化取决于几个关键残基，并为突变体在生理温度下结合丧失提供了合理的解释。这些发现可能为突变体结构提供一种挽救策略。
