title: A specificity-enhancing factor for the ClpXP degradation machine.
abstract: Events that stall bacterial protein synthesis activate the ssrA-tagging machinery, resulting in resumption of translation and addition of an 11-residue peptide to the carboxyl terminus of the nascent chain. This ssrA-encoded peptide tag marks the incomplete protein for degradation by the energy-dependent ClpXP protease. Here, a ribosome-associated protein, SspB, was found to bind specifically to ssrA-tagged proteins and to enhance recognition of these proteins by ClpXP. Cells with an sspB mutation are defective in degrading ssrA-tagged proteins, demonstrating that SspB is a specificity-enhancing factor for ClpXP that controls substrate choice.
authors.affiliation: Department of Biology and Howard Hughes Medical Institute, Building 68, Room 523, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
authors.forename: I
authors.initials: I
authors.lastname: Levchenko
authors.forename: M
authors.initials: M
authors.lastname: Seidel
authors.forename: R T
authors.initials: RT
authors.lastname: Sauer
authors.forename: T A
authors.initials: TA
authors.lastname: Baker
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D049071:Endopeptidase Clp; D004926:Escherichia coli / Q000201:enzymology / Q000378:metabolism*; D029968:Escherichia coli Proteins; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000378:metabolism; D009154:Mutation; D009842:Oligopeptides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009876:Operon; D012270:Ribosomes / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008164:Luminescent Proteins; D009842:Oligopeptides; C072071:SspA protein, E coli; D049452:Green Fluorescent Proteins; D012697:Serine Endopeptidases; C483573:ClpXP protease, E coli; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases