Nucleic Acids Research Advance Access published online on February 19, 2008
Nucleic Acids Research, doi:10.1093/nar/gkn067
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Molecular Biology |
Binding of sulphonated indigo derivatives to RepA-WH1 inhibits DNA-induced protein amyloidogenesis
1Department of Molecular Microbiology, 2Department of Protein Science, Centro de Investigaciones Biológicas (CSIC), C/ Ramiro de Maeztu, 9. E-28040 and 3Structural Biology and Biocomputing Programme, Centro Nacional de Investigaciones Oncológicas (CNIO), C/ Melchor Fernández Almagro, 3. E-28029 Madrid, Spain
*To whom correspondence should be addressed. Tel: +34 91 8373112; Fax: +34 91 5360432; Email: rgiraldo{at}cib.csic.es
Received November 19, 2007. Revised January 9, 2008. Accepted February 1, 2008.
The quest for inducers and inhibitors of protein amyloidogenesis is of utmost interest, since they are key tools to understand the molecular bases of proteinopathies such as Alzheimer, Parkinson, Huntington and Creutzfeldt–Jakob diseases. It is also expected that such molecules could lead to valid therapeutic agents. In common with the mammalian prion protein (PrP), the N-terminal Winged-Helix (WH1) domain of the pPS10 plasmid replication protein (RepA) assembles in vitro into a variety of amyloid nanostructures upon binding to different specific dsDNA sequences. Here we show that di- (S2) and tetra-sulphonated (S4) derivatives of indigo stain dock at the DNA recognition interface in the RepA-WH1 dimer. They compete binding of RepA to its natural target dsDNA repeats, found at the repA operator and at the origin of replication of the plasmid. Calorimetry points to the existence of a major site, with micromolar affinity, for S4-indigo in RepA-WH1 dimers. As revealed by electron microscopy, in the presence of inducer dsDNA, both S2/S4 stains inhibit the assembly of RepA-WH1 into fibres. These results validate the concept that DNA can promote protein assembly into amyloids and reveal that the binding sites of effector molecules can be targeted to inhibit amyloidogenesis.