read-through (B) were measured by dual luciferase gain-of-function assays using wild-type mitohybrid ribosomes n=4 read-through), mutant A1555G mitohybrid ribosomes n=4 read-through), E. coli wild-type ribosomes (n=9), E.coli mutant A127Y ribosomes (n=9), M. smegmatis merodiploid wild-type ribosomes (n=9), and M. smegmatis merodiploid mutant S152Y ribosomes (n=9). To determine read-through the Asp357 (GAC codon) of the F-luc gene was replaced by the nonsense TGA stop codon. Results are derived by calculating mutant hFluc/hRluc activity related to wild-type hFluc/hRluc activity. 