A surprising finding of the last years was the demonstration that the LepA protein is a novel elongation factor of the ribosome. LepA is one of the most conserved proteins and present in all bacteria and mitochondria. This protein is essential for cell viability at low pH’s in the media together with a high ionic strength, where without LepA translocation is impaired leading to an increase in misreading and eventually blocking of polysomes. Elucidating the mechanism led to another surprise, namely a novel function: LepA back-translocates defective translocated ribosomes. In other words, the results suggest that LepA recognizes ribosomes after a defective translocation reaction and induces a back translocation giving EF-G a second chance to translocate the tRNAs correctly. Therefore, we suggest calling LepA “elongation factor 4 (EF4)” (2006; 1).