title: Utilization of synthetic peptides to evaluate the importance of substrate interaction at the proteolytic site of Escherichia coli Lon protease.
abstract: Lon, also known as protease La, is an ATP-dependent protease functioning to degrade many unstructured proteins. Currently, very little is known about the substrate determinants of Lon at the proteolytic site. Using synthetic peptides constituting different regions of the endogenous protein substrate lambdaN, we demonstrated that the proteolytic site of Escherichia coli Lon exhibits a certain level of localized sequence specificity. Using an alanine positional scanning approach, we discovered a set of discontinuous substrate determinants surrounding the scissile Lon cleavage site in a model peptide substrate, which function to influence the k(cat) of the peptidase activity of Lon. We further investigated the mode of peptide interaction with the proteolytically inactive Lon mutant S679A in the absence and presence of ADP or AMPPNP by 2-dimensional nuclear magnetic resonance spectroscopy, and discovered that the binding interaction between protein and peptide varies with the nucleotide bound to the enzyme. This observation is suggestive of a substrate translocation step, which likely limits the turnover of the proteolytic reaction. The contribution of the identified substrate determinants towards the kinetics of ATP-dependent degradation of lambdaN and truncated lambdaN mutants by Lon was also examined. Our results indicated that Lon likely recognizes numerous discontinuous substrate determinants throughout lambdaN to achieve substrate promiscuity.
authors.affiliation: Department of Chemistry, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-7078, USA.
authors.forename: Jessica
authors.initials: J
authors.lastname: Patterson-Ward
authors.forename: Johnathan
authors.initials: J
authors.lastname: Tedesco
authors.forename: Jason
authors.initials: J
authors.lastname: Hudak
authors.forename: Jennifer
authors.initials: J
authors.lastname: Fishovitz
authors.forename: James
authors.initials: J
authors.lastname: Becker
authors.forename: Hilary
authors.initials: H
authors.lastname: Frase
authors.forename: Kirsten
authors.initials: K
authors.lastname: McNamara
authors.forename: Irene
authors.initials: I
authors.lastname: Lee
mesh_terms: D000409:Alanine / Q000235:genetics; D000595:Amino Acid Sequence; D020134:Catalytic Domain; D004926:Escherichia coli / Q000201:enzymology*; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism; D049070:Protease La / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017384:Sequence Deletion; D013379:Substrate Specificity; D054334:Viral Regulatory and Accessory Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: C059417:N protein, Bacteriophage lambda; D010455:Peptides; D054334:Viral Regulatory and Accessory Proteins; D049070:Protease La; D000409:Alanine