ERROR-PRONE EF-TU-REDUCES INVIVO ENZYME-ACTIVITY AND CELLULAR GROWTH-RATE

Mutations in Salmonella typhimurium encoding errorprone EF-Tu (tufA8, tufB103) enhance translational error levels and also cause a reduced growth rate. The relative changes in error level and growth rate are inversely related and dependent on the status of the two tuf genes. Possible causes of the reduced growth rate were investigated. Several important parameters with the potential to alter growth rate (the EF-Tu-ribosome interaction, the in vivo elongation rate and the processivity of translation), are all relatively unaffected by the tuf mutations. The small reduction in processivity observed in some strains is not quantitatively related to the growth rate reduction. Instead, the error-enhancing mutations are associated with a large reduction in the specific activity of a test protein, beta-galactosidase, suggesting by inference that the reduced growth rate is a consequence of the synthesis of error-containing proteins.