Elongation Factor 4 (EF4), also known as ​​LepA​​, is a highly conserved ​​GTPase translation factor​​ present across bacteria, mitochondria, and chloroplasts. It regulates protein synthesis by interacting with the ribosome during translation elongation. Unlike canonical elongation factors (e.g., EF-G) that promote forward translocation, EF4 catalyzes ​​back-translocation of tRNAs​​ on the ribosome, effectively acting as a molecular ’reverse gear‘ to reposition tRNAs and mRNA. This unique function allows EF4 to maintain translational fidelity under stress conditions (e.g., low pH or high ionic strength) by rescuing stalled ribosomes and correcting errors in protein synthesis.