Investigating the Intrinsic Aggregation Potential of Evolutionarily Conserved Segments in p53

Protein aggregation and amyloid formation are known to play a role both in diseases and in biological functions. Transcription factor p53 plays a major role in tumor suppression by maintaining genomic stability. Recent studies have suggested that amyloid formation of p53 could lead to its loss of physiological function as a tumor suppressor. Here, we investigated the intrinsic amyloidogenic nature of wild-type p53 using sequence analysis. We used bioinformatics and aggregation prediction algorithms to establish the evolutionarily conserved nature of aggregation-prone sequences in wild-type p53. Further, we analyzed the amyloid forming capacity of conserved and aggregation-prone p53-derived peptides PILTIITL and YFTLQI <i>in vitro</i> using various biophysical techniques, including all atom molecular dynamics simulation. Finally, we probed the seeding ability of the PILTIITL peptide on p53 aggregation <i>in vitro</i> and in cells. Our data demonstrate the intrinsic amyloid forming ability of a sequence stretch of the p53 DNA binding domain (DBD) and its aggregation templating behavior on full-length and p53 core domain. Therefore, p53 aggregation, instigated through an amyloidogenic segment in its DBD, could be a putative driving force for p53 aggregation <i>in vivo</i>

Binary Short-Range Colloidal Assembly of Magnetic Iron Oxides Nanoparticles and Fullerene (nC₆₀) in Environmental Media

Colloidal assembly of nC₆₀ fullerene with naturally abundant magnetic iron oxide NPs will affect their fate and transformation in environmental media. In solution, fullerene association to aggregating iron oxide NPs/clusters greatly enhanced the overall colloidal stability. Development of depletion-mediated structured fullerene layers between pure and surface modified γFe₂O₃ NPs possibly resulted in such stabilization. Here, we also report that on air–water interface, association of fullerene to pure and humic acid (HA7) coated γFe₂O₃ NPs led to the formation of ordered assemblies, e.g., binary wires and closed-packed “crystalline” and “glassy” structures in the presence and absence of electrolytes suggesting immobilization of the former. The interaction of fullerene to Fe₃O₄ NPs and clusters also produced ordered assemblies along with amorphous aggregates. Fullerene interaction with Fe₃O₄ NPs in low concentration of HA1 and Na⁺ at pH 6 formed dendritic growth and polycrystalline circular assemblies on air–water interface. HRTEM study further revealed that the monolayer circular assemblies were highly ordered but structural degeneracy was evident in multilayers. Therefore, interfacial assemblies of fullerene with iron oxide NPs resulted in short-range periodic structures with concomitant immobilization and reduction in availability of the former, especially in soils or sediments rich in the latter

The Parkinson’s Disease-Associated H50Q Mutation Accelerates α‑Synuclein Aggregation <i>in Vitro</i>

α-Synuclein (α-Syn) aggregation is directly linked with Parkinson’s disease (PD) pathogenesis. Here, we analyzed the aggregation of newly discovered α-Syn missense mutant H50Q <i>in vitro</i> and found that this mutation significantly accelerates the aggregation and amyloid formation of α-Syn. This mutation, however, did not alter the overall secondary structure as suggested by two-dimensional nuclear magnetic resonance and circular dichroism spectroscopy. The initial oligomerization study by cross-linking and chromatographic techniques suggested that this mutant oligomerizes to an extent similar to that of the wild-type α-Syn protein. Understanding the aggregation mechanism of this H50Q mutant may help to establish the aggregation and phenotypic relationship of this novel mutant in PD