title: Flexible linkers leash the substrate binding domain of SspB to a peptide module that stabilizes delivery complexes with the AAA+ ClpXP protease.
abstract: SspB dimers bind proteins bearing the ssrA-degradation tag and stimulate their degradation by the ClpXP protease. Here, E. coli SspB is shown to contain a dimeric substrate binding domain of 110-120 N-terminal residues, which binds ssrA-tagged substrates but does not stimulate their degradation. The C-terminal 40-50 residues of SspB are unstructured but are required for SspB to form substrate-delivery complexes with ClpXP. A synthetic peptide containing the 10 C-terminal residues of SspB binds ClpX, stimulates its ATPase activity, and prevents SspB-mediated delivery of GFP-ssrA for ClpXP degradation. This tripartite structure--an ssrA-tag binding and dimerization domain, a flexible linker, and a short peptide module that docks with ClpX--allows SspB to deliver tagged substrates to ClpXP without interfering with their denaturation or degradation.
authors.affiliation: Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Wah
authors.forename: Igor
authors.initials: I
authors.lastname: Levchenko
authors.forename: Gabrielle E
authors.initials: GE
authors.lastname: Rieckhof
authors.forename: Daniel N
authors.initials: DN
authors.lastname: Bolon
authors.forename: Tania A
authors.initials: TA
authors.lastname: Baker
authors.forename: Robert T
authors.initials: RT
authors.lastname: Sauer
mesh_terms: D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000737:chemistry*; D000255:Adenosine Triphosphate / Q000378:metabolism; D018829:Adhesins, Bacterial / Q000737:chemistry* / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000502:physiology; D001665:Binding Sites; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D049071:Endopeptidase Clp; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins; D049452:Green Fluorescent Proteins; D006868:Hydrolysis; D008164:Luminescent Proteins / Q000378:metabolism; D008954:Models, Biological; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012329:RNA, Bacterial / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000737:chemistry*; D013379:Substrate Specificity
chemical_list: D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008164:Luminescent Proteins; D018832:Molecular Chaperones; D012329:RNA, Bacterial; C096222:tmRNA; C068465:salivary agglutinin receptor, Streptocococcus; D049452:Green Fluorescent Proteins; D000255:Adenosine Triphosphate; 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