Conformational priming of RepA-WH1 for functional amyloid conversion detected by NMR spectroscopy

29 p.-6 fig.-1 tab.
How proteins with a stable globular fold acquire the amyloid state is still largely unknown. RepA, a versatile plasmidic DNA binding protein from Pseudomonas savastanoi, is functional as a transcriptional repressor or as an initiator or inhibitor of DNA replication, the latter via assembly of an amyloidogenic oligomer. Its N-terminal domain (WH1) is responsible for discrimination between these functional abilities by undergoing insufficiently understood structural changes. RepA-WH1 is a stable dimer whose conformational dynamics had not been explored. Here, we have studied it through NMR {1H}-15N relaxation and H/D exchange kinetics measurements. The N- and the C-terminal α-helices, and the internal amyloidogenic loop, are partially unfolded in solution. S4-indigo, a small inhibitor of RepA-WH1 amyloidogenesis, binds to and tethers the N-terminal α-helix to a β-hairpin that is involved in dimerization, thus providing evidence for a priming role of fraying ends and dimerization switches in the amyloidogenesis of folded proteins.
This work was supported by grants SAF2016-76678-C2-2-R (DVL), CTQ2017-84371-P (Mª Ángeles Jiménez), BIO2015-68730-R (R.G.), BFU2015-72271-EXP (R.G.) and RTI2018-094549-B-I00 (R.G.) from the Spanish Ministry of Innovation and Competitiveness. NMR experiments were performed in the‘‘Manuel Rico’’ NMR laboratory (LMR) of the Spanish National Research Coun-cil (CSIC), a node of the Spanish Large-Scale National Facility (ICTS R-LRB)