Effect of Mutation on an Aggregation-Prone Segment of p53: From Monomer to Dimer to Multimer

Protein aggregation and amyloid formation are implicated in many diseases as well as in other biological phenomena. Recent studies have suggested that amyloid formation of tumor suppressor p53 can lead to loss of its physiological function, resulting in accelerated cancer progression. Design of cancer therapeutics, therefore, requires understanding of the mechanism of pS3 aggregation. Here, we have employed atomistic simulations to characterize the aggregation process of the aggregation-prone (as suggested by experimental studies) p53 fragment (LTIITLE, 252-258) and to assess the efficiency of its I254R mutant as an aggregation suppressor. We show that the wild-type sequence attains stable beta-sheet rich structure in the parallely arranged dimeric form, which dissociates in a sequential manner under mechanical force. The wild-type sequence further displays high aggregation propensity self-assembling into structures with parallel peptide arrangement. The I254R mutation destabilizes the dimer, changes the mechanical dissociation of the dimer to cooperative unfolding, reduces the aggregation propensity of the sequence, and alters the relative orientation of the peptides in the aggregate. Addition of the wild-type sequence, however, partially restores the aggregation propensity of the I254R mutant.