title: Depletion of the signal recognition particle receptor inactivates ribosomes in Escherichia coli.
abstract: The signal recognition particle (SRP)-dependent cotranslational targeting of proteins to the cytoplasmic membrane in bacteria or the endoplasmic reticulum membrane in eukaryotes is an essential process in most living organisms. Eukaryotic cells have been shown to respond to an impairment of the SRP pathway by (i) repressing ribosome biogenesis, resulting in decreased protein synthesis, and (ii) by increasing the expression of protein quality control mechanisms, such as chaperones and proteases. In the current study, we have analyzed how bacteria like Escherichia coli respond to a gradual depletion of FtsY, the bacterial SRP receptor. Our analyses using cell-free transcription/translation systems showed that FtsY depletion inhibits the translation of both SRP-dependent and SRP-independent proteins. This synthesis defect is the result of a multifaceted response that includes the upregulation of the ribosome-inactivating protein ribosome modulation factor (RMF). Although the consequences of these responses in E. coli are very similar to some of the effects also observed in eukaryotic cells, one striking difference is that E. coli obviously does not reduce the rate of protein synthesis by downregulating ribosome biogenesis. Instead, the upregulation of RMF leads to a direct and reversible inhibition of translation.
authors.affiliation: Institut für Biochemie und Molekularbiologie, ZBMZ, Albert-Ludwigs Universität Freiburg, Stefan-Meier-Strasse 17, D-79104 Freiburg, Germany.
authors.forename: Jonas
authors.initials: J
authors.lastname: Bürk
authors.forename: Benjamin
authors.initials: B
authors.lastname: Weiche
authors.forename: Meike
authors.initials: M
authors.lastname: Wenk
authors.forename: Diana
authors.initials: D
authors.lastname: Boy
authors.forename: Sigrun
authors.initials: S
authors.lastname: Nestel
authors.forename: Bernd
authors.initials: B
authors.lastname: Heimrich
authors.forename: Hans-Georg
authors.initials: HG
authors.lastname: Koch
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics / Q000502:physiology; D002479:Inclusion Bodies / Q000235:genetics / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000502:physiology*; D012269:Ribosomal Proteins / Q000235:genetics / Q000502:physiology; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C087406:FtsY protein, Bacteria; D018160:Receptors, Cytoplasmic and Nuclear; D012269:Ribosomal Proteins; C063545:ribosome modulation factor, E coli