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

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.