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Articles by X. Feng
Total Records ( 2 ) for X. Feng
  Y Xue , S Wang and X. Feng
 

Site-specific recognition and DNA-binding activity of p53 are crucial for its tumour suppressor function. Previous reports have shown that metal ions can affect the specific recognition and DNA-binding activity of p53DBD. Here we firstly report that magnesium ion can bind to the protein and influence its DNA-binding activity. To elucidate the nature and the effect of metal ions in the reaction chemistry, we utilized endogenous tryptophan fluorescence to quantitate the interaction between p53DBD and metal ions. The Ka value for the binding of Mg2+ to the protein is 1.88 x 103 M–1. Analysis of the CD data clearly suggested that the binding of magnesium ion induced a subtle conformational change rather than a radical modification of the overall protein architecture. Based on the results of electrophoretic mobility shift assays and fluorescence experiments, we concluded that the binding of Mg2+ significantly stimulated the binding of the protein to DNA in a sequence-independent manner, which differed from that of zinc ions in a sequence-specific manner. Based on these results and the fact that Mg2+ exists at relatively high concentration in the cell, we propose that Mg2+ is one of potential factors to affect or regulate the transactivation of p53.

  Y Xue , S Wang and X. Feng
 

The tumour suppressor protein p53 is a sequence-specific transcription factor that coordinates one molecule of zinc in the core domain. In our recent study, magnesium can also bind to the p53DBD and enhance its DNA-binding activity. In this study, a systematic analysis of the conformation and stability changes induced by these two metal ions was reported. The spectra of protein intrinsic fluorescence were used to measure the equilibrium unfolding of the p53DBD protein. The stability against chemical denaturation increased in the order apo < Mg2+ < Zn2+. The thermal stability monitored by DSC scans showed that the binding of metal ions to p53DBD increased the thermal stability of the protein. To explore additional information of structural changes after the binding of metal ions, we used the fluorescent probes to evaluate the hydrophobic surface exposure. The results established that metal ions binding increased hydrophobic exposure on the surface of p53DBD. Analysis of acrylamide quenching experiments revealed that the binding of metal ions to p53DBD induced a structural modification of the protein and this change provided significant protection against acrylamide quenching. Overall, the present results indicated that p53DBD underwent a conformational change upon the binding of metal ions, which was characterized by an increased stability of the protein.

 
 
 
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