title: Deciphering the Roles of Multicomponent Recognition Signals by the AAA+ Unfoldase ClpX.
abstract: ATP-dependent protein remodeling and unfolding enzymes are key participants in protein metabolism in all cells. How these often-destructive enzymes specifically recognize target protein complexes is poorly understood. Here, we use the well-studied AAA+ unfoldase-substrate pair, Escherichia coli ClpX and MuA transposase, to address how these powerful enzymes recognize target protein complexes. We demonstrate that the final transposition product, which is a DNA-bound tetramer of MuA, is preferentially recognized over the monomeric apo-protein through its multivalent display of ClpX recognition tags. The important peptide tags include one at the C-terminus ("C-tag") that binds the ClpX pore and a second one (enhancement or "E-tag") that binds the ClpX N-terminal domain. We construct a chimeric protein to interrogate subunit-specific contributions of these tags. Efficient remodeling of MuA tetramers requires ClpX to contact a minimum of three tags (one C-tag and two or more E-tags), and that these tags are contributed by different subunits within the tetramer. The individual recognition peptides bind ClpX weakly (KD>70 μM) but impart a high-affinity interaction (KD~1.0 μM) when combined in the MuA tetramer. When the weak C-tag signal is replaced with a stronger recognition tag, the E-tags become unnecessary and ClpX's preference for the complex over MuA monomers is eliminated. Additionally, because the spatial orientation of the tags is predicted to change during the final step of transposition, this recognition strategy suggests how AAA+ unfoldases specifically distinguish the completed "end-stage" form of a particular complex for the ideal biological outcome.
authors: Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, 68-132, Cambridge, MA 02139, USA.
authors: Lorraine
authors: L
authors: Ling
authors: Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, W225, Chicago, IL 60637, USA.
authors: Sherwin P
authors: SP
authors: Montaño
authors: Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, 68-132, Cambridge, MA 02139, USA.
authors: Robert T
authors: RT
authors: Sauer
authors: Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, W225, Chicago, IL 60637, USA.
authors: Phoebe A
authors: PA
authors: Rice
authors: Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, 68-132, Cambridge, MA 02139, USA; Howard Hughes Medical Institute, 4000 Jones Bridge Road, Chevy Chase, MD 20815-6789, USA. Electronic address: tabaker@mit.edu.
authors: Tania A
authors: TA
authors: Baker
mesh_terms: D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D049071:Endopeptidase Clp / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli / Q000737:chemistry / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D046911:Macromolecular Substances / Q000378:metabolism; D018832:Molecular Chaperones / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D017510:Protein Folding; D021122:Protein Subunits / Q000737:chemistry; D021381:Protein Transport
chemical_list: D029968:Escherichia coli Proteins; D046911:Macromolecular Substances; D018832:Molecular Chaperones; D021122:Protein Subunits; D000255:Adenosine Triphosphate; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases; C088072:ClpX protein, E coli; D000074183:ATPases Associated with Diverse Cellular Activities
keywords: ClpXP; MuA protein; adaptor protein; chaperone; degron