Proposed pore-like structure of the pseudosymmetrical region (Agmon et al. 2005; Agmon 2009; Rivas and Fox 2020) and the tt_P1 construct (Bose et al. 2021, 2022). Both were modeled over the crystallographic structure of T. thermophilus (PDB ID 4WPO, Lin et al. 2015). (A) P- and A-regions (green and blue, respectively) hybridize together to form a heterodimer with a pore-like structure that enhances peptide bond formation, as it occurs in the extant ribosomal region called the peptidyl transferase center or PTC. (B) Space-filled structural model of two tt_P1 constructs highlighted in two tonalities of green, hypothetically dimerized into a similar pore-like structure that is also able to enhance peptide bond formation. Structure was obtained by structural superposition of a second tt_P1 element over the original A-region RNA as described in the Materials and Methods section.
