title: Effects of inorganic polyphosphate on the proteolytic and DNA-binding activities of Lon in Escherichia coli.
abstract: Lon belongs to a unique group of proteases that bind to DNA and is involved in the regulation of several important cellular functions, including adaptation to nutritional downshift. Previously, we revealed that inorganic polyphosphate (polyP) increases in Escherichia coli in response to amino acid starvation and that it stimulates the degradation of free ribosomal proteins by Lon. In this work, we examined the effects of polyP on the proteolytic and DNA-binding activities of Lon. An order-of-addition experiment suggested that polyP first binds to Lon, which stimulates Lon-mediated degradation of ribosomal proteins. A polyP-binding assay using Lon deletion mutants showed that the polyP-binding site of Lon is localized in the ATPase domain. Because the same ATPase domain also contains the DNA-binding site, polyP can compete with DNA for binding to Lon. In fact, an equimolar amount of polyP almost completely inhibited DNA-Lon complex formation, suggesting that Lon binds to polyP with a higher affinity than it binds to DNA. Collectively, our results showed that polyP may control the cellular activity of Lon not only as a protease but also as a DNA-binding protein.
authors.affiliation: Department of Molecular Biotechnology, Hiroshima University, Hiroshima 739-8530, Japan.
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Nomura
authors.forename: Junichi
authors.initials: J
authors.lastname: Kato
authors.forename: Noboru
authors.initials: N
authors.lastname: Takiguchi
authors.forename: Hisao
authors.initials: H
authors.lastname: Ohtake
authors.forename: Akio
authors.initials: A
authors.lastname: Kuroda
mesh_terms: D049069:ATP-Dependent Proteases; D002352:Carrier Proteins / Q000378:metabolism; D002850:Chromatography, Gel; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D017931:DNA Primers / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D017353:Gene Deletion; D006360:Heat-Shock Proteins / Q000378:metabolism; D058619:Maltose-Binding Proteins; D009154:Mutation; D010710:Phosphates; D017856:Phosphotransferases (Phosphate Group Acceptor); D011122:Polyphosphates / Q000737:chemistry*; D049070:Protease La; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012269:Ribosomal Proteins / Q000737:chemistry; D012270:Ribosomes / Q000737:chemistry; D017422:Sequence Analysis, DNA; D012697:Serine Endopeptidases / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D017931:DNA Primers; D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; D058619:Maltose-Binding Proteins; D010710:Phosphates; D011122:Polyphosphates; D012269:Ribosomal Proteins; D004247:DNA; D017856:Phosphotransferases (Phosphate Group Acceptor); D049069:ATP-Dependent Proteases; D012697:Serine Endopeptidases; C483567:Lon protein, E coli; D049070:Protease La