title: Cleavage site selection within a folded substrate by the ATP-dependent lon protease.
abstract: Mechanistic studies of ATP-dependent proteolysis demonstrate that substrate unfolding is a prerequisite for processive peptide bond hydrolysis. We show that mitochondrial Lon also degrades folded proteins and initiates substrate cleavage non-processively. Two mitochondrial substrates with known or homology-derived three-dimensional structures were used: the mitochondrial processing peptidase alpha-subunit (MPPalpha) and the steroidogenic acute regulatory protein (StAR). Peptides generated during a time course of Lon-mediated proteolysis were identified and mapped within the primary, secondary, and tertiary structure of the substrate. Initiating cleavages occurred preferentially between hydrophobic amino acids located within highly charged environments at the surface of the folded protein. Subsequent cleavages proceeded sequentially along the primary polypeptide sequence. We propose that Lon recognizes specific surface determinants or folds, initiates proteolysis at solvent-accessible sites, and generates unfolded polypeptides that are then processively degraded.
authors.affiliation: Institute of Molecular Biology, Slovak Academy of Sciences, 84551 Bratislava, Slovak Republic.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Ondrovicová
authors.forename: Tong
authors.initials: T
authors.lastname: Liu
authors.forename: Kamalendra
authors.initials: K
authors.lastname: Singh
authors.forename: Bin
authors.initials: B
authors.lastname: Tian
authors.forename: Hong
authors.initials: H
authors.lastname: Li
authors.forename: Oleksandr
authors.initials: O
authors.lastname: Gakh
authors.forename: Dusan
authors.initials: D
authors.lastname: Perecko
authors.forename: Jirí
authors.initials: J
authors.lastname: Janata
authors.forename: Zvi
authors.initials: Z
authors.lastname: Granot
authors.forename: Joseph
authors.initials: J
authors.lastname: Orly
authors.forename: Eva
authors.initials: E
authors.lastname: Kutejová
authors.forename: Carolyn K
authors.initials: CK
authors.lastname: Suzuki
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry*; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019295:Computational Biology; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D013058:Mass Spectrometry; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D010749:Phosphoprotein Phosphatases / Q000737:chemistry; D010750:Phosphoproteins / Q000737:chemistry; D049070:Protease La / Q000737:chemistry; D011485:Protein Binding; D017510:Protein Folding; D000071636:Protein Phosphatase 2C; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013379:Substrate Specificity; D013997:Time Factors; D000098682:Steroidogenic Acute Regulatory Protein
chemical_list: D005656:Fungal Proteins; D010455:Peptides; D010750:Phosphoproteins; D011506:Proteins; D000098682:Steroidogenic Acute Regulatory Protein; D000255:Adenosine Triphosphate; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C; D049070:Protease La