title: Structural analysis of the adaptor protein ClpS in complex with the N-terminal domain of ClpA.
abstract: In Escherichia coli, protein degradation is performed by several proteolytic machines, including ClpAP. Generally, the substrate specificity of these machines is determined by chaperone components, such as ClpA. In some cases, however, the specificity is modified by adaptor proteins, such as ClpS. Here we report the 2.5 A resolution crystal structure of ClpS in complex with the N-terminal domain of ClpA. Using mutagenesis, we demonstrate that two contact residues (Glu79 and Lys 84) are essential not only for ClpAS complex formation but also for ClpAPS-mediated substrate degradation. The corresponding residues are absent in the chaperone ClpB, providing a structural rationale for the unique specificity shown by ClpS despite the high overall similarity between ClpA and ClpB. To determine the location of ClpS within the ClpA hexamer, we modeled the N-terminal domain of ClpA onto a structurally defined, homologous AAA+ protein. From this model, we proposed a molecular mechanism to explain the ClpS-mediated switch in ClpA substrate specificity.
authors.affiliation: MPI für Biochemie, Abteilung Membranbiochemie, Am Klopferspitz 18a, D-82152 Martinsried, Germany. zeth@biochem.mpg.de
authors.forename: Kornelius
authors.initials: K
authors.lastname: Zeth
authors.forename: Raimond B
authors.initials: RB
authors.lastname: Ravelli
authors.forename: Klaus
authors.initials: K
authors.lastname: Paal
authors.forename: Stephen
authors.initials: S
authors.lastname: Cusack
authors.forename: Bernd
authors.initials: B
authors.lastname: Bukau
authors.forename: David A
authors.initials: DA
authors.lastname: Dougan
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000378:metabolism*; D000595:Amino Acid Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism* / Q000502:physiology; D018360:Crystallography, X-Ray; D049071:Endopeptidase Clp; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism* / Q000502:physiology; D046911:Macromolecular Substances; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D002352:Carrier Proteins; C454820:ClpS protein, E coli; D029968:Escherichia coli Proteins; D046911:Macromolecular Substances; D012697:Serine Endopeptidases; C483568:ClpA protease, E coli; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases