title: Post-translational modification of RNase R is regulated by stress-dependent reduction in the acetylating enzyme Pka (YfiQ).
abstract: RNase R is a processive exoribonuclease that plays an important role in degradation of structured RNAs in Escherichia coli. RNase R is unstable in exponential phase cells; however, under certain stress conditions, RNase R levels increase dramatically due to its stabilization. Binding of tmRNA and SmpB to the C-terminal region of RNase R is required for its instability, and this binding is regulated by acetylation of a single residue, Lys544, in exponential phase cells. RNase R is not acetylated in stationary phase. We show here that only exponential phase RNase R is acetylated because the modifying enzyme, protein lysine acetyltransferase, Pka (YfiQ), is absent from late exponential and stationary phase cells. As a consequence, newly synthesized RNase R remains unmodified. Together with the turnover of preexisting acetylated RNase R, no modified RNase R remains in stationary phase. We find that RNase R in cold-shocked cells also lacks the acetyl modification due to the absence of Pka. These data indicate that RNase R stability depends on Pka, which itself is regulated under stress conditions.
authors: Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, Florida 33101, USA.
authors: Wenxing
authors: W
authors: Liang
authors: Murray P
authors: MP
authors: Deutscher
mesh_terms: D000123:Acetyltransferases / Q000378:metabolism*; D004795:Enzyme Stability; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029968:Escherichia coli Proteins / Q000378:metabolism*; D005095:Exoribonucleases / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D012329:RNA, Bacterial / Q000378:metabolism; D013312:Stress, Physiological
chemical_list: D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; C096222:tmRNA; D000123:Acetyltransferases; C561243:acetyl-CoA synthetase acetylase, E coli; D005095:Exoribonucleases; C080868:ribonuclease R