title: M domains couple the ClpB threading motor with the DnaK chaperone activity.
abstract: The AAA(+) chaperone ClpB mediates the reactivation of aggregated proteins in cooperation with the DnaK chaperone system. ClpB consists of two AAA domains that drive the ATP-dependent threading of substrates through a central translocation channel. Its unique middle (M) domain forms a coiled-coil structure that laterally protrudes from the ClpB ring and is essential for aggregate solubilization. Here, we demonstrate that the conserved helix 3 of the M domain is specifically required for the DnaK-dependent shuffling of aggregated proteins, but not of soluble denatured substrates, to the pore entrance of the ClpB translocation channel. Helix 3 exhibits nucleotide-driven conformational changes possibly involving a transition between folded and unfolded states. This molecular switch controls the ClpB ATPase cycle by contacting the first ATPase domain and establishes the M domain as a regulatory device that acts in the disaggregation process by coupling the threading motor of ClpB with the DnaK chaperone activity.
authors.affiliation: ZMBH, Universität Heidelberg, Im Neuenheimer Feld 282, Heidelberg D-69120, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Haslberger
authors.forename: Jimena
authors.initials: J
authors.lastname: Weibezahn
authors.forename: Regina
authors.initials: R
authors.lastname: Zahn
authors.forename: Sukyeong
authors.initials: S
authors.lastname: Lee
authors.forename: Francis T F
authors.initials: FT
authors.lastname: Tsai
authors.forename: Bernd
authors.initials: B
authors.lastname: Bukau
authors.forename: Axel
authors.initials: A
authors.lastname: Mogk
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D049071:Endopeptidase Clp; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000378:metabolism; D020409:Molecular Motor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D016963:Thermus thermophilus / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D020409:Molecular Motor Proteins; D000255:Adenosine Triphosphate; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases; C063842:dnaK protein, E coli; C069775:ClpB protein, E coli