Aggregation of the neuronal protein α-synuclein into amyloid fibrils plays a central role in the development of Parkinson’s disease. Growth of fibrils can be suppressed by blocking fibril ends from their interaction with monomeric proteins. In this work, we constructed inhibitors that bind to the ends of α-synuclein amyloid fibrils with very high affinity. They are based on synthetic α-synuclein dimers and interact with fibrils via two monomeric subunits adopting conformation that efficiently blocks fibril elongation. By tuning the charge of dimers, we further enhanced the binding affinity and prepared a construct that inhibits fibril elongation at nanomolar concentration (IC50 ≈ 20 nM). To the best of our knowledge, it is the most efficient inhibitor of α-synuclein fibrillization.

We synthesized solvatochromic thiol‐reactive fluorescent probes 6FM‐M and 7AFM‐M possessing two‐band emission. 7AFM‐M was designed to have a smaller dipole moment than 6FM‐M and as a result it showed better separation of the two emission bands. Both probes were used to label a cysteine mutant of α‐synuclein (αSyn), a presynaptic neuronal protein associated with Parkinson's disease. We investigated the ability of the probes to sense αSyn binding to lipid membranes and αSyn fibrillization, and compared their sensitivity with that of one‐band solvatochromic probes. We found that while all the tested probes can discriminate two αSyn states, only the 7AFM‐M probe is able to clearly discriminate all three protein states of αSyn: unstructured, membrane‐bound and fibrillar αSyn. Finally, using αSyn labelled with 7AFM‐M, we demonstrated that high density of αSyn on lipid membranes may lead to the partial membrane destruction with a formation of lipoprotein particles.

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Tumor suppressor Partner and Localizer of BRCA2 (PALB2) is a scaffold protein that links BRCA1, BRCA2 and other DNA repair factors and plays a crucial role in homologous recombination (HR). The interaction of PALB2 with DNA strongly enhances the efficiency of HR. Importantly, the PALB2 DNA-binding domain (PALB2-DBD) supports strand exchange of DNA or RNA, a complex multistep reaction carried by only a few protein families like RecA-like recombinases or Rad52. The mechanisms of PALB2 DNA binding and strand exchange are unknown. Through circular dichroism, electron paramagnetic spectroscopy and small-angle X-ray scattering, we found that the PALB2-DBD is intrinsically disordered, even when bound to DNA. Intrinsically disordered proteins (IDPs) are prevalent in the human proteome and have many important biological functions. The advanced level of complexity of the strand exchange reaction significantly expands the functional repertoire of IDPs. Using confocal single-molecule FRET, we found that PALB2-DBD binding leads to oligomerization-dependent compaction of DNA. We hypothesize that PALB2-DBD uses a chaperone-like mechanism to aid formation and resolution of complex DNA and RNA multichain intermediates during DNA replication and repair. Similar DNA-binding IDRs may represent a novel class of functional domains evolved in eukaryotic nucleic acids metabolism complexes.