Trans-targeting of the phage Mu repressor is promoted by conformational changes that expose its ClpX recognition determinant.
Dominant negative forms of the phage Mu repressor, including the mutant Vir repressors, are not only rapidly degraded by the ClpXP protease but also promote degradation of the unmodified, wild-type repressor. This trans-targeting of the wild-type repressor depends upon a determinant within its C-terminal domain, which is needed for recognition by ClpX. An environmentally sensitive fluorescent probe (2-(4'-maleimidylanilino)naphthalene-6-sulfonic acid (MIANS)) attached to the C terminus of the full-length repressor indicated that Vir induces the movement of this domain into a more exposed configuration. Vir also promoted attachment of MIANS to the C terminus of the repressor at an accelerated rate, and it greatly increased the rate of phosphorylation of a cAMP-dependent protein kinase motif attached to the repressor C terminus. While an excess of Vir was needed to promote repressor phosphorylation at maximal rates, the presence of ClpX could increase phosphorylation rates at lower Vir levels. trans-Targeting of the Mu repressor is therefore promoted by exposing its ClpX recognition determinant, and the action of ClpX can assist Vir in exposing these determinants.
Marshall-Batty
Kimberly R
KR
Department of Biochemistry and Molecular Biology, Georgetown University Medical Center, Washington, DC 20057, USA.
Nakai
Hiroshi
H
D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000595:Amino Acid Sequence; D000817:Anilino Naphthalenesulfonates; D010583:Bacteriophage mu / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D017931:DNA Primers; D049071:Endopeptidase Clp; D029968:Escherichia coli Proteins; D005456:Fluorescent Dyes; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012097:Repressor Proteins / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
D000817:Anilino Naphthalenesulfonates; D017931:DNA Primers; D029968:Escherichia coli Proteins; D005456:Fluorescent Dyes; D018832:Molecular Chaperones; D012097:Repressor Proteins; C021310:2-(4'-maleimidylanilino)naphthalene-6-sulfonic acid; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases; C088072:ClpX protein, E coli; D000074183:ATPases Associated with Diverse Cellular Activities