Ribose 2′-hydroxyl groups in the 5′ strand of the acceptor arm of P-site tRNA are not essential for EF-G catalyzed translocation

The coupled movement of tRNA-mRNA complex through the ribosome is a fundamental step during the protein elongation process. We demonstrate that the ribosome will translocate a P-site-bound tRNA Met with a break in the phosphodiester backbone between positions 17 and 18 in the D-loop. Crystallographic data showed that the acceptor arms of P- and E-site tRNA interact extensively with the ribosomal large subunit. Therefore, we used this fragmented P-site-bound tRNA Met to investigate the contributions of single 2' -hydroxyl groups in the 5' strand of the acceptor arm for translocation into the ribosomal E-site. EF-G-dependent translocation of the tRNAs was monitored using a toeprinting assay and a fluorescence-based rapid kinetic method. Surprisingly, our results show that none of the 2' -hydroxyl groups in the 5' strand of the acceptor arm of P-site-bound tRNA Met between positions 1-17 play a critical role during translocation. This suggests that either these 2' hydroxyl groups are not important for translocation or they are redundant and the three-dimensional shape of the P- site tRNA is more important for translocation.