| Summary: | 碩士 === 國立中興大學 === 生命科學系所 === 101 === p53 is a tumor suppressor protein which plays an important role in regulating the cell cycle. Its pathway is activated in response to a variety of cell stresses such as oncogene activating, DNA damage, hypoxia and other stress signals. By inducing apoptosis of these abnormal cells (tumor cells), p53 can inhibit tumor cells proliferation. Hence, p53 is also called "genome guardian" due to its ability of preventing genome mutations. According to the literature (Petitjean et al., 2007), p53 missense substitutions might cause many types of cancer, indicating these mutants might have distinct structures and impaired function comparing to wild type p53. Here, we aim to study how these mutations affect the secondary, tertiary and quaternary structure of p53 protein. We choose eight significant hot-spot mutants (R175H, R248W, R248Q, G245S, R249S, R273C, R273H, R282W) which are frequently found in cancer patients. In this study, the biophysical methods such as Circular Dichroism (CD), fluorescence and analytical ultracentrifugation (AUC) were utilized to analyze the structural differences between human p53 wild-type (WT) and mutant proteins. We found that the thermal stability of p53 mutants is relatively lower than that of WT. Besides, the mutations R175H, R249S, and R282W showed significant changes on the tertiary structure, which was monitored by intrinsic fluorescence and ANS (8-Anilinonaphthalene-1-Sulfonic Acid) fluorescence. Furthermore, the mutants R175H, R249S, and R282W have distinct quaternary structures, which were measured by sedimentation velocity. In conclusion, our data suggested that R175H, R249S and R282W may lead to a significant alteration of p53 structure and its stability.
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