Degradation of carboxy-terminal-tagged cytoplasmic proteins by the Escherichia coli protease HflB (FtsH).
Proteins with short nonpolar carboxyl termini are unstable in Escherichia coli. This proteolytic pathway is used to dispose of polypeptides synthesized from truncated mRNA molecules. Such proteins are tagged with an 11-amino-acid nonpolar destabilizing tail via a mechanism involving the 10Sa (SsrA) stable RNA and then degraded. We show here that the ATP-dependent zinc protease HflB (FtsH) is involved in the degradation of four unstable derivatives of the amino-terminal domain of the lambdacI repressor: three with nonpolar pentapeptide tails (cI104, cI105, cI108) and one with the SsrA tag (cI-SsrA). cI105 and cI-SsrA are also degraded by the ClpP-dependent proteases. Loss of ClpP can be compensated for by overproducing HflB. In an in vitro system, cI108 and cI-SsrA are degraded by HflB in an energy-dependent reaction, indicating that HflB itself recognizes the carboxyl terminus. These results establish a tail-specific pathway for removing abnormal cytoplasmic proteins via the HflB and Clp proteases.
Herman
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C
Université Libre de Bruxelles, B-1640 Rhode-Saint-Genèse, Belgium. lherman@itsa.ucsf.edu
Thévenet
D
D
Bouloc
P
P
Walker
G C
GC
D'Ari
R
R
D049069:ATP-Dependent Proteases; D000251:Adenosine Triphosphatases; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D003593:Cytoplasm / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D049071:Endopeptidase Clp; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D014644:Genetic Variation; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism; D013379:Substrate Specificity; D013696:Temperature
D001426:Bacterial Proteins; D017931:DNA Primers; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D012329:RNA, Bacterial; C096222:tmRNA; D049069:ATP-Dependent Proteases; C513383:FtsH protein, E coli; D012697:Serine Endopeptidases; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases