title: Trans-targeting of protease substrates by conformationally activating a regulable ClpX-recognition motif.
abstract: Conversion of bacteriophage Mu repressor to ClpXP-sensitive form correlates with induced local flexibility at the ClpX recognition motif located at the C-terminal end. Changing the C-terminal valine to an alanine (RepV196A) caused the degradation tag to be constitutively active like that of mutant repressors called Vir, which have a dominant ClpXP-sensitive conformation. However, unlike Vir, RepV196A was unable to convert wild-type repressor (Rep) to the ClpXP-sensitive form. In mixtures with Rep, only RepV196A was rapidly degraded by ClpXP. Unlike Rep, RepV196A was ClpXP sensitive without induced C-terminal flexibility. And unlike adaptor proteins that tether and deliver substrates to ClpX for trans-targeting, Vir promoted rapid degradation of Rep by ClpX deleted for the tethering site that binds adaptor proteins. Therefore, Rep's ClpX recognition motif has regulable properties, allowing an alternative trans-targeting mechanism in which an inactive degradation tag is turned on by induced conformational changes.
authors.affiliation: Department of Biochemistry and Molecular & Cellular Biology, Georgetown University Medical Center, Rm. 331 Basic Science Bldg., 3900 Reservoir Rd. NW, Washington, DC 20057-1455, 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 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020816:Amino Acid Motifs; D010583:Bacteriophage mu / Q000235:genetics / Q000378:metabolism*; D049071:Endopeptidase Clp / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018832:Molecular Chaperones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D012097:Repressor Proteins / Q000737:chemistry / 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