tREPs-A New Class of Functional tRNA-Encoded Peptides

We asked if transfer RNA (tRNA) ever got an opportunity of translating its own sequence during evolution, what would have been the function of such tRNA-encoded peptides (tREPs)? If not, could one artificially synthesize tREPs to study the corresponding functional outcomes? Here, we report a novel, first-in-the-class, chemically synthesized tREP-18 molecule originating from the Escherichia coli tRNA sequence showing potent antileishmanial property. As a first step, E. coli tRNAs were computationally translated into peptide sequence equivalents and a database of full-length hypothetical tREPs was created. The tREP sequences were sent into sequence, structure, and energy filters to narrow down potential peptides for experimental validation. Based on the functional predictions, tREPs were screened against antiparasitic targets, leading to the identification of tREP-18 as a potential antiparasitic peptide. The in vitro assay of chemically synthesized tREP-18 on the Ag83 strain of Leishmania donovani showed its potent antileishmanial property (IC50 value of 22.13 nM). The atomic force microscopy and scanning electron microscopy images indicated significant alteration in the cytoskeletal architecture of tREP-18-treated parasites. Also, tREP-18 seems to destabilize the mitochondrial membrane potential of parasites, disrupting their cellular integrity and leading to parasitic death. The cellular assays of the tREP-18 peptide on the BS12 strain, a clinical isolate of post-kala azar dermal leishmaniasis, demonstrated its significant efficacy at an IC50 value of 15 nM. The tREP-18 peptide showed a toxic effect on the amastigote stage of the parasite, showing macrophage pathogen clearance at a concentration of 22.5 nM. This study provides the proof of the concept of making a new class of functional peptides from tRNA sequences. It also opens a huge untapped tRNA-peptide space toward novel discoveries and applications. In the future, it would be interesting to perform tREP edits and redesign tREPs toward specific applications.