title: Protein unfolding and degradation by the AAA+ Lon protease.
abstract: AAA+ proteases employ a hexameric ring that harnesses the energy of ATP binding and hydrolysis to unfold native substrates and translocate the unfolded polypeptide into an interior compartment for degradation. What determines the ability of different AAA+ enzymes to unfold and thus degrade different native protein substrates is currently uncertain. Here, we explore the ability of the E. coli Lon protease to unfold and degrade model protein substrates beginning at N-terminal, C-terminal, or internal degrons. Lon has historically been viewed as a weak unfoldase, but we demonstrate robust and processive unfolding/degradation of some substrates with very stable protein domains, including mDHFR and titin(I27) . For some native substrates, Lon is a more active unfoldase than related AAA+ proteases, including ClpXP and ClpAP. For other substrates, this relationship is reversed. Thus, unfolding activity does not appear to be an intrinsic enzymatic property. Instead, it depends on the specific protease and substrate, suggesting that evolution has diversified rather than optimized the protein unfolding activities of different AAA+ proteases.
authors.affiliation: Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel. gure@bgu.ac.il
authors.forename: Eyal
authors.initials: E
authors.lastname: Gur
authors.forename: Marina
authors.initials: M
authors.lastname: Vishkautzan
authors.forename: Robert T
authors.initials: RT
authors.lastname: Sauer
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D064211:Connectin; D004526:Efficiency; D029968:Escherichia coli Proteins / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008954:Models, Biological; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D009124:Muscle Proteins / Q000737:chemistry / Q000378:metabolism; D010447:Peptide Hydrolases / Q000737:chemistry / Q000378:metabolism; D049070:Protease La / Q000378:metabolism*; D011489:Protein Denaturation; D017510:Protein Folding; D011494:Protein Kinases / Q000737:chemistry / Q000378:metabolism; D055503:Protein Multimerization / Q000502:physiology; D017434:Protein Structure, Tertiary; D059748:Proteolysis; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism
chemical_list: D064211:Connectin; D029968:Escherichia coli Proteins; D046912:Multiprotein Complexes; D009124:Muscle Proteins; D011993:Recombinant Fusion Proteins; C577285:TTN protein, human; D013762:Tetrahydrofolate Dehydrogenase; D011494:Protein Kinases; D010447:Peptide Hydrolases; C483567:Lon protein, E coli; D049070:Protease La