title: Addiction protein Phd of plasmid prophage P1 is a substrate of the ClpXP serine protease of Escherichia coli.
abstract: Plasmid-encoded addiction genes augment the apparent stability of various low copy number bacterial plasmids by selectively killing plasmid-free (cured) segregants or their progeny. The addiction module of plasmid prophage P1 consists of a pair of genes called phd and doc. Phd serves to prevent host death when the prophage is retained and, should retention mechanisms fail, Doc causes death on curing. Doc acts as a cell toxin to which Phd is an antidote. In this study we show that host mutants with defects in either subunit of the ClpXP protease survive the loss of a plasmid that contains a P1 addiction module. The small antidote protein Phd is fully stable in these two mutant hosts, whereas it is labile in a wild-type host. We conclude that the role of ClpXP in the addiction mechanism of P1 is to degrade the Phd protein. This conclusion situates P1 among plasmids that elicit severe withdrawal symptoms and are able to do so because they encode both a cell toxin and an actively degraded macromolecule that blocks the synthesis or function of the toxin.
authors.affiliation: Laboratory of Biochemistry, National Cancer Institute, Bethesda, MD 20892-4255, USA.
authors.forename: H
authors.initials: H
authors.lastname: Lehnherr
authors.forename: M B
authors.initials: MB
authors.lastname: Yarmolinsky
mesh_terms: D018528:ATP-Binding Cassette Transporters; D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D017101:Bacteriophage P1 / Q000235:genetics; D001483:Base Sequence; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics; D049071:Endopeptidase Clp; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins; D058619:Maltose-Binding Proteins; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins; D010957:Plasmids / Q000235:genetics*; D011533:Proviruses / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis; D012697:Serine Endopeptidases / Q000378:metabolism*; D013379:Substrate Specificity; D014764:Viral Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*
chemical_list: D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D058619:Maltose-Binding Proteins; D018832:Molecular Chaperones; D009004:Monosaccharide Transport Proteins; C083665:Phd protein, Enterobacteria phage P1; D011994:Recombinant Proteins; D014764:Viral Proteins; C461599:maltose transport system, E coli; D012697:Serine Endopeptidases; C483573:ClpXP protease, E coli; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases; C088072:ClpX protein, E coli; D000074183:ATPases Associated with Diverse Cellular Activities