title: Communication of ClpXP protease hypersensitivity to bacteriophage Mu repressor isoforms.
abstract: The immunity repressor (Rep) of bacteriophage Mu establishes and maintains lysogeny by shutting down transposition functions needed for phage DNA replication. Although Rep is stable in vivo, an altered immunity repressor (Vir) encoded by virulent, trans-dominant Mu mutants is rapidly degraded by Escherichia coli ClpXP protease. Rep and Vir are degraded at approximately the same maximal velocity (Vmax) by ClpXP, but the Km for Rep (3.6 microM) is over 20-fold higher than the Km for Vir (0.15 microM). Rep is also highly resistant to degradation in the presence of DNA whereas Vir is not. Vir increases the rate of Rep degradation by reducing its Km and imparts to Rep ClpXP sensitivity in the presence of DNA. Vir can drive at an accelerated rate the complete degradation of Rep molecules that outnumber Vir by eightfold or more. So long as Vir is present at a concentration of 0.1 microM or higher, Rep is degraded with a Km that is indistinguishable from that of Vir. These characteristics of repressor may be an important means of transducing physiological signals that induce Mu transposition in response to growth conditions or environmental stress, ClpXP hypersensitivity being disseminated among Rep molecules for the induction of Mu transposition.
authors.affiliation: Department of Biochemistry and Molecular Biology, Georgetown University Medical Center, 3900 Reservoir Rd NW, Washington, DC 20007, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Welty
authors.forename: J M
authors.initials: JM
authors.lastname: Jones
authors.forename: H
authors.initials: H
authors.lastname: Nakai
mesh_terms: D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D010583:Bacteriophage mu / Q000235:genetics / Q000378:metabolism*; D004247:DNA; D049071:Endopeptidase Clp; D029968:Escherichia coli Proteins; D007536:Isomerism; D007700:Kinetics; D018832:Molecular Chaperones; D009154:Mutation; D009875:Operator Regions, Genetic; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; D012097:Repressor Proteins; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins; D004247:DNA; D012697:Serine Endopeptidases; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases; C088072:ClpX protein, E coli; D000074183:ATPases Associated with Diverse Cellular Activities