MRC Laboratory of Molecular Biology, Cambridge, UK.
J Mol Biol. 2011 Jun 10;409(3):358-68. doi: 10.1016/j.jmb.2011.03.047. Epub 2011 Mar 30.
The tetrameric tumor suppressor p53 plays a pivotal role in the control of the cell cycle and provides a paradigm for an emerging class of oligomeric, multidomain proteins with structured and intrinsically disordered regions. Many of its biophysical and functional properties have been extrapolated from truncated variants, yet the exact structural and functional role of certain segments of the protein is unclear. We found from NMR and X-ray crystallography that the DNA-binding domain (DBD) of human p53, usually defined as residues 94-292, extends beyond these domain boundaries. Trp91, in the hinge region between the disordered proline-rich N-terminal domain and the DBD, folds back onto the latter and has a cation-π interaction with Arg174. These additional interactions increase the melting temperature of the DBD by up to 2 °C and inhibit aggregation of the p53 tetramer. They also modulate the dissociation of the p53 tetramer. The absence of the Trp91/Arg174 packing presumably allows nonnative DBD-DBD interactions that both nucleate aggregation and stabilize the interface. These data have important implications for studies of multidomain proteins in general, highlighting the fact that weak ordered-disordered domain interactions can modulate the properties of proteins of complex structure.
四聚体肿瘤抑制因子 p53 在细胞周期的控制中起着关键作用，并为新兴的寡聚、多结构域蛋白类提供了范例，这些蛋白具有结构和固有无序区域。其许多生物物理和功能特性都是从截短变体推断出来的，但该蛋白的某些片段的确切结构和功能作用尚不清楚。我们通过 NMR 和 X 射线晶体学发现，人 p53 的 DNA 结合域（DBD）通常定义为残基 94-292，超出了这些结构域的边界。位于无序脯氨酸丰富的 N 端结构域和 DBD 之间的铰链区域的色氨酸 91 回折到后者上，并与精氨酸 174 形成阳离子-π 相互作用。这些额外的相互作用将 DBD 的熔点提高了 2°C，抑制了 p53 四聚体的聚集。它们还调节 p53 四聚体的解离。Trp91/Arg174 包装的缺失可能允许非天然 DBD-DBD 相互作用，这些相互作用既能引发聚集，又能稳定界面。这些数据对一般的多结构域蛋白研究具有重要意义，突出了一个事实，即弱的有序-无序结构域相互作用可以调节复杂结构蛋白的性质。
