title: Activation of a dormant ClpX recognition motif of bacteriophage Mu repressor by inducing high local flexibility.
abstract: The C-terminal domain (CTD) of bacteriophage Mu immunity repressor (Rep) regulates DNA binding by the N-terminal domain and degradation by ClpXP protease. Five residues at the Rep C terminus (CTD5) can serve as a ClpX recognition motif, but it is dormant unless activated, a state that can be induced by the presence of dominant-negative mutant repressors (Vir). Conversion of Rep to ClpXP-sensitive form was associated with not only increased exposure of CTD5 to solvent but also increased CTD motion or flexibility as measured by fluorescence anisotropy. CTD mutations (V183S, K193S, and V196S) promoting ClpXP resistance without destroying the recognition motif prevented increased CTD motion induced by Vir. Suppression of ClpXP protease resistance conferred by the V196S mutation also correlated with restoration of CTD motion. The temperature-sensitive R47Q mutation present in cis within the DNA-binding domain restored ClpXP protease sensitivity to the V196S mutant, and anisotropy analysis indicated that R47Q allows the V196S CTD to gain increased flexibility when Vir was present. The results indicate that the CTD functions to turn the recognition motif on and off, most likely by modulating flexibility of the domain that harbors the ClpX recognition motif, suggesting a general mechanism by which proteins can regulate their own degradation.
authors.affiliation: Department of Biochemistry and Molecular & Cellular Biology, Georgetown University Medical Center, 3900 Reservoir Road NW, Washington, D. C. 20057, USA.
authors.forename: Kimberly R
authors.initials: KR
authors.lastname: Marshall-Batty
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nakai
mesh_terms: D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D020816:Amino Acid Motifs / Q000502:physiology; D010583:Bacteriophage mu / Q000235:genetics / Q000378:metabolism*; D049071:Endopeptidase Clp / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism* / Q000821:virology; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D020125:Mutation, Missense; D017434:Protein Structure, Tertiary / Q000502:physiology; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; D012097:Repressor Proteins; D014764:Viral Proteins; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases; C088072:ClpX protein, E coli; D000074183:ATPases Associated with Diverse Cellular Activities