Fig. 2: Cryo-EM structures of ORF2p core in apo, ssRNA and RNA:DNA hybrid-bound states.
From: Structures, functions and adaptations of the human LINE-1 ORF2 protein
a, ORF2p is unstable in the absence of nucleic acids (Tm = 34.1 °C ± 0.35) but is significantly stabilized by the binding of ssRNA (Tm = 47.5 °C ± 0.32) and RNA:DNA heteroduplex (Tm = 50.2 °C ± 0.1) as determined by differential scanning fluorimetry. b, Density map of the 3.3 Å cryo-EM reconstruction of the ORF2p core in ternary complex with RNA template–DNA primer heteroduplex and dTTP, coloured by proximity to modelled domains with fit atomic model (inset left), which shows clear density for primer, template and dTTP base for addition. Deviation of RNA template (inset right) in the ssRNA cryo-EM structure (purple) from the heteroduplex (grey, backbone RMSD of 3.76 Å). c, Structural schematic of the contacts between the PIP box (inset left) and baseplate (inset right) subdomains of the ORF2p tower with the canonical RT subdomains of palm and fingers. d, Denaturing gel RT assay with ORF2p core (wild type; WT) or tower deletions (∆302–363, ∆302–389) shows similar RT activity with and without the tower and tower lock. Data are representative of three (a) and two (d) independent experiments.
