Panos Spatharas @pspatharas.bsky.social · 14/10/20269/11 Across the homologues we examined, RcaTs that form tetramers or larger assemblies are toxic and occupy distinct phylogenetic clades from non-toxic, dimeric RcaTs. This links differences in toxicity to an intrinsic protein property: the capacity to oligomerise. 112
Panos Spatharas @pspatharas.bsky.social · 14/10/20267/11 Together, our findings support a model in which methylation promotes msDNA disengagement, exposing the previously occluded dimer–dimer interface. This allows RcaT tetramerisation and activation, coupled to retron complex disassembly. 112
Panos Spatharas @pspatharas.bsky.social · 14/10/20266/11 All these assemblies form through the same dimer–dimer interface (a), which was occluded in the intact retron complex. Mutations that disrupt this interface abolish RcaT toxicity (b), showing that assembly beyond a dimer is essential for its activity. 112
Panos Spatharas @pspatharas.bsky.social · 14/10/20265/11 We next examined RcaT after release. It forms tetramers consisting of two stacked dimers, with additional dimers stacking to form higher-order oligomers. 112
Panos Spatharas @pspatharas.bsky.social · 14/10/20264/11 In these assemblies, RcaT directly contacts the msDNA methylation site (a). Methylation promotes complex disassembly and partial release of RcaT (b). 112
Panos Spatharas @pspatharas.bsky.social · 14/10/20263/11 Our cryo-EM structure reveals RcaT encased as an inactive dimer within a four-component core retron complex that can further assemble into filaments. 142
Panos Spatharas @pspatharas.bsky.social · 14/10/20269/11 Across the homologues we examined, RcaTs that form tetramers or larger assemblies are toxic and occupy distinct phylogenetic clades from non-toxic, dimeric RcaTs. This links differences in toxicity to an intrinsic protein property: the capacity to oligomerise. 000
Panos Spatharas @pspatharas.bsky.social · 14/10/20267/11 Together, our findings support a model in which methylation promotes msDNA displacement, exposing the previously occluded dimer–dimer interface. This allows RcaT tetramerisation and activation, coupled to retron complex disassembly. 100
Panos Spatharas @pspatharas.bsky.social · 14/10/20266/11 All these assemblies form through the same dimer–dimer interface (a), which was occluded in the intact retron complex. Mutations that disrupt this interface abolish RcaT toxicity (b), showing that assembly beyond a dimer is essential for its activity. 100
Panos Spatharas @pspatharas.bsky.social · 14/10/20265/11 We next examined RcaT after release. It forms tetramers consisting of two stacked dimers, with additional dimers stacking to form higher-order oligomers. 100
Panos Spatharas @pspatharas.bsky.social · 14/10/20264/11 In these assemblies, RcaT directly contacts the msDNA methylation site (a). Methylation promotes complex disassembly and partial release of RcaT (b). 100
Panos Spatharas @pspatharas.bsky.social · 14/10/20263/11 Our cryo-EM structure reveals RcaT encased as an inactive dimer within a four-component core retron complex that can further assemble into filaments. 100