The T box riboswitch regulates many amino acid-related genes in Gram-positive bacteria.  T box riboswitch-mediated gene regulation usually occurs at the level of transcription attenuation via structural rearrangements in the 5’ untranslated (leader) region of the mRNA in response to binding of a specific uncharged tRNA.  We recently identified a novel group of ileS T box leader sequences in organisms of the phylum Actinobacteria.  The Stem I domains of these RNAs lack several highly conserved elements that are essential for interaction with the tRNA ligand in other T box RNAs.  These ileS RNAs are unusual in that they are predicted to regulate gene expression at the level of translation initiation, through tRNA-dependent stabilization of a helix that sequesters a sequence complementary to the Shine-Dalgarno (SD) sequence, thus freeing the SD sequence for ribosome binding and translation initiation.  We have demonstrated that RNAs in this class are functional translational riboswitches, and identify novel tRNA-riboswitch interactions that are important for tRNA recognition.