Simultaneous binding of two proteins to opposite sides of a single transfer RNA

Transfer RNA (tRNA) is a small nucleic acid (typically 76 nucleotides) that forms binary complexes with proteins, such as aminoacyl tRNA synthetases ( RS) and Trbp111. The latter is a widely distributed structure-specific tRNA -binding protein that is incorporated into cell signaling molecules. The st ructure of Trbp111 was modeled onto to the outer, convex side of the L-shap ed tRNA. Here we present RNA footprints that are consistent with this model . This binding mode is in contrast to that of tRNA synthetases, which bind to the inside, or concave side, of tRNA These opposite locations of binding for these two proteins suggest the possibility of a ternary complex. The f ormation of a tRNA synthetase-tRNA-Trbp111 ternary complex was detected by two independent methods. The results indicate that the tRNA is sandwiched b etween the two protein molecules. A thermodynamic and functional analysis i s consistent with the tRNA retaining its native structure in the ternary co mplex. These results may have implications for how the translation apparatu s is linked to other cellular machinery.