1.
SynBio and the Boundaries between Functional and Pathogenic RepA-WH1 Bacterial Amyloids.
Abstract:
Amyloids are protein polymers that were initially linked to human diseases. Across the whole Tree of Life, many disease-unrelated proteins are now emerging for which amyloids represent distinct functional states. Most bacterial amyloids described are extracellular, contributing to biofilm formation. However, only a few have been found in the bacterial cytosol. This paper reviews from the perspective of synthetic biology (SynBio) our understanding of the subtle line that separates functional from pathogenic and transmissible amyloids (prions). In particular, it is focused on RepA-WH1, a functional albeit unconventional natural amyloidogenic protein domain that participates in controlling DNA replication of bacterial plasmids. SynBio approaches, including protein engineering and the design of allosteric effectors such as diverse ligands and an optogenetic module, have enabled the generation in RepA-WH1 of an intracellular cytotoxic prion-like agent in bacteria. The synthetic RepA-WH1 prion has the potential to develop into novel antimicrobials.
2.
Optogenetic Navigation of Routes Leading to Protein Amyloidogenesis in Bacteria.
Abstract:
Modulation of liquid-liquid and liquid-hydrogel phase transitions is central to avoid the cytotoxic aggregation of proteins in eukaryotic cells, but knowledge on its relevance in bacteria is limited. Here the power of optogenetics to engineer proteins as light-responsive switches has been used to control the balance between solubility and aggregation for LOV2-WH1, a chimera between the plant blue light-responsive domain LOV2 and the bacterial prion-like protein RepA-WH1. These proteins were first linked by fusing, as a continuous α-helix, the C-terminal photo-transducer Jα helix in LOV2 with the N-terminal domain-closure α1 helix in RepA-WH1, and then improved for light-responsiveness by including mutations in the Jα moiety. In the darkness and in a crowded solution in vitro, LOV2-WH1 nucleates the irreversible assembly of amyloid fibers into a hydrogel. However, under blue light illumination LOV2-WH1 assembles as soluble oligomers. When expressed in Escherichia coli, LOV2-WH1 forms in the darkness large intracellular amyloid inclusions compatible with bacterial proliferation. Strikingly, under blue light LOV2-WH1 aggregates decrease in size while they become detrimental for bacterial growth. LOV2-WH1 optogenetics governs the assembly of mutually exclusive inert amyloid fibers or cytotoxic oligomers, thus enabling the navigation of the conformational landscape of protein amyloidogenesis to generate potential photo-activated anti-bacterial devices (optobiotics).
