Voyage of RepA protein from plasmid DNA replication through amyloid aggregation towards synthetic biology

Abstract

DNA replication of plasmids in Gram-negative bacteria has been an object of study at CIB-CSIC for nearly 30 years. We have been focused on the enterobacterial antibiotic resistance factor R1 (1981-1992) and the pPS10 replicon from the phytopathogen Pseudomonas savastanoi (since 1984). Our group has used multidisciplinary (genetic, biochemical and biophysical-structural) approaches to unravel the molecular mechanism for the activation of RepA. Rep-type plasmidic proteins are either transcriptional repressors or replication initiators/inhibitors, depending on their association state (dimers vs. monomers) and targeting of alternative (operator or iteron) DNA sites. We discovered that allosteric DNA-binding remodels the structure of RepA N-terminal domain (WH1), transforming α-helical portions into β-strands. This precisely tunes the distances between the DNA reading heads in WH1 and the C-terminal domain (WH2), to match the target operator or iteron sequences. We have recently moved into engineering such structural transformation in RepA-WH1 to build-up synthetic protein devices that allow for customized ligand (DNA)-promoted amyloidogenesis. Our basic studies on plasmid DNA replication are relevant for settling the bases of a minimalist bacterial model to tackle transmissible amyloid proteinopathies and are a valuable tool for bottom-up synthetic biology.