Movement of tRNA and mRNA through the ribosome is coupled. However, selection for suppression of a -1 frameshift mutation in Escherichia coli has yielded a class of mutant tRNAs that can violate this mechanism and "hop" or disengage from their cognate codons and re-pair downstream in the mRNA. Previously described tRNA mutants of this class included those with insertions in the anticodon of tRNA(Val)1. This report describes further tRNA(Val)1 alterations that enhance hopping; these include a novel insertion in the anticodon loop, base substitutions in the anticodon stem and a base deletion in the variable loop. These results indicate that several different features of a tRNA are important for maintaining stable codon-anticodon interactions and coupled movement of tRNA and mRNA during the elongation phase of protein synthesis.