| Abstract
| - Maintaining the native conformation is essential for the proper function of tumor suppressorprotein p53. However, p53 is a low-stability protein that can easily lose its function upon structuralperturbations such as those resulting from missense mutations, leading to the development of cancer.Therefore, it is important to develop strategies to design stable p53 which still maintains its normal function.Here, we compare the stabilities of the human and worm p53 core domains using molecular dynamicssimulations. We find that the worm p53 is significantly more stable than the human form. Detailed analysisof the structural fluctuations shows that the stability difference lies in the peripheral structural motifs thatcontrast in their structural features and flexibility. The most dramatic difference in stability originatesfrom loop L1, from the turn between helix H1 and β-strand S5, and from the turn that connects β-strandsS7 and S8. Structural analysis shows significant differences for these motifs between the two proteins.Loop L1 lacks secondary structure, and the turns between helix H1 and strand S5 and between strands S7and S8 are much longer in the human form p53. On the basis of these differences, we designed a mutantby shortening the turn between strands S7 and S8 to enhance the stability. Surprisingly, this mutant wasvery stable when probed by molecular dynamics simulations. In addition, the stabilization was not localizedin the turn region. Loop L1 was also significantly stabilized. Our results show that stabilizing peripheralstructural motifs can greatly enhance the stability of the p53 core domain and therefore is likely to be aviable alternative in the development of stable p53. In addition, loop- or turn-related mutants with differentstabilities may also be used to probe the relationship between function, a particular structural motif, andits flexibility.
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