Different conformations of tRNA in the ribosomal P‐site and A‐site

Publisher Website
Google Scholar
Abstract
Footprinting studies involving radioactively end-labeled tRNA species bound at either the ribosomal P- or A-site have yielded information that the tRNA''s conformation is different in the two sites. Appropriate controls showed the relevance of using poly(U)-directed tRNAPhe binding in the P-site and Phe-tRNAPhe in the A-site. Digestion of the tRNA species was effected by RNAases T1, T2 and cobra venom RNase. Experiments were performed with tRNAs 32P-labeled at either end to establish positions of primary cuts more confidently. In addition to the common protection of the aminoacyl-stem and anticodon-arm, footprinting experiments revealed striking differences in the accessibility of the T- and D-loops of tRNAs bound in the P- and A-sites. We observed a more open structure for the tRNA in the A-site. These results are consistent with a dynamic structure of tRNA during the translocation step of protein biosynthesis.