The p53 core domain is a molten globule at low pH: functional implications of a partially unfolded structure.
The p53 core domain is a molten globule at low pH: functional implications of a partially unfolded structure.
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p53核心结构域是低pH值的熔融球体：部分展开的结构的功能含义。
DOI：
10.1074/jbc.m109.075861
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发表时间：
2010-01-22
期刊：
影响因子：
--
通讯作者：
Silva JL
中科院分区：
文献类型：
--
作者：
Bom AP;Freitas MS;Moreira FS;Ferraz D;Sanches D;Gomes AM;Valente AP;Cordeiro Y;Silva JL
p53是一种维持基因组完整性的转录因子，其功能在50%的人类癌症中丧失。大多数p53突变聚集在核心结构域内。在这里，我们研究了低pH对野生型（wt）p53核心结构域（p53 C）和R248 Q突变体的结构的影响。在低pH下，色氨酸残基部分暴露于溶剂，表明三级结构波动。另一方面，二级结构增加，如通过圆二色性所确定的。探针双ANS的结合（双-8-苯胺基萘-1-磺酸盐）表明在低pH下野生型和突变型p53 C的疏水口袋暴露增加。这种行为伴随着尿素变性下缺乏协同性和当p53 C处于酸性pH时压力下稳定性降低。这些结果表明p53 C在低pH（5.0）下获得部分未折叠的构象（熔融球状态）。该构象的流体动力学性质介于天然构象和变性构象之间。1H-15 N HSQC NMR光谱证实，与pH 7.2相比，该蛋白质在酸性pH下具有典型的熔融球结构。用p53-GFP转染的培养的人乳腺细胞（MCF-7）揭示了p53在酸性囊泡中的定位，表明细胞中存在低pH构象。低pH胁迫也倾向于有利于细胞中高水平的p53。总之，所有这些数据表明，p53可能在酸性微环境中发挥生理或病理作用。
p53 is a transcription factor that maintains genome integrity, and its function is lost in 50% of human cancers. The majority of p53 mutations are clustered within the core domain. Here, we investigate the effects of low pH on the structure of the wild-type (wt) p53 core domain (p53C) and the R248Q mutant. At low pH, the tryptophan residue is partially exposed to the solvent, suggesting a fluctuating tertiary structure. On the other hand, the secondary structure increases, as determined by circular dichroism. Binding of the probe bis-ANS (bis-8-anilinonaphthalene-1-sulfonate) indicates that there is an increase in the exposure of hydrophobic pockets for both wt and mutant p53C at low pH. This behavior is accompanied by a lack of cooperativity under urea denaturation and decreased stability under pressure when p53C is in acidic pH. Together, these results indicate that p53C acquires a partially unfolded conformation (molten-globule state) at low pH (5.0). The hydrodynamic properties of this conformation are intermediate between the native and denatured conformation. 1H-15N HSQC NMR spectroscopy confirms that the protein has a typical molten-globule structure at acidic pH when compared with pH 7.2. Human breast cells in culture (MCF-7) transfected with p53-GFP revealed localization of p53 in acidic vesicles, suggesting that the low pH conformation is present in the cell. Low pH stress also tends to favor high levels of p53 in the cells. Taken together, all of these data suggest that p53 may play physiological or pathological roles in acidic microenvironments.