PNNL

Abstract

N??-lysine acetylation is a common post-translational modification observed in diverse species of bacteria. Aside from a few central metabolic enzymes and transcription factors, little is known about how this post-translational modification regulates protein activity. In this work, we investigated how lysine acetylation affects translation in Escherichia coli. In multiple species of bacteria, ribosomal proteins are highly acetylated at conserved lysine residues, suggesting that this modification may regulate translation. In support of this hypothesis, we found that the addition of the acetyl donors, acetyl phosphate or acetyl-Coenzyme A, inhibits translation but not transcription using an E. coli cell-free system. Further investigations using in vivo assays revealed that acetylation does not appear to alter the rate of translation elongation but rather inhibits ribosome subunit association, which is inhibited in mutants or growth conditions known to promote lysine acetylation. Furthermore, ribosomal proteins are more acetylated in the disassociated 30S and 50S ribosomal subunit than in the fully assembled 70S complex, suggesting that acetylation inhibits association of the ribosomal subunits during translation initiation. The effect of acetylation is also growth rate dependent, with disassociation of the subunits most pronounced during late exponential and early stationary phase growth – the same growth phase where protein acetylation is greatest. Collectively, our data demonstrate that lysine acetylation inhibits translation, most likely by preventing subunit association. These results have also uncovered a new mechanism for coupling translation to the metabolic state of the cell.