Fig. 2: YheS interactions with the ribosome and P-tRNA.

a, b The Arm subdomain of YheS interacts with both the protein (uL1, a) and RNA (helix H76 of 23S rRNA, b) components of the L1-stalk. c The residues at the base of PtIM form multiple polar interactions with the 23S rRNA near the L1-stalk. d NBD1 of YheS interacts with ribosomal protein uS7 in the SSU head. e, f PtIM of YheS forms multiple polar interactions with the 23S rRNA near the PTC. g, h Interactions between YheS and P-tRNA. NBD2 of YheS forms hydrogen bonds and stacking interactions with the P-tRNA elbow g, while the tip of PtIM forms two hydrogen bonds with the 3′ end of the P-tRNA h. i Relocation of the P-tRNA upon YheS binding. The P-tRNA in the present complex with YheS is colored green, while that of the SecM-arrested ribosome without YheS and that of the canonical elongating ribosome (PDB: 8B0X)⁴⁵ are shown in gray and black, respectively. j Conformational comparison of the P-tRNA and SecM nascent chain between the SecM-arrested ribosome with or without YheS. In the YheS-bound state, the 3′ end of the P-tRNA and the attached SecM nascent chain are retracted by ~2 Å toward the tunnel entrance.