Alterations in ribosomal protein L19 that decrease the fidelity of translation.

Ribosomal protein L19 is an essential ribosomal protein and is a component of bridge B8, one of the protein-RNA bridges linking the large and small ribosomal subunits. Bridge B8 also contributes to the accuracy of translation by affecting GTPase activation by ribosome-bound aminoacyl tRNA-EF-Tu•GTP ternary complexes. Previous work has identified a limited number of accuracy-altering alterations in protein L19 of Salmonella enterica and Thermus thermophilus. Here, we have targeted the Escherichia coli rplS gene encoding L19 for mutagenesis and have screened for mutants with altered levels of miscoding. We have recovered 14 distinct L19 mutants, all of which promote increased stop codon readthrough, but do not have major effects on subunit association or cell growth. Examination of the E. coli 70S ribosome structure indicates that the amino acid substitutions cluster in three distinct regions of L19 and thereby potentially affect its interactions with L14 and 16S rRNA.