title: The inhibitory form of NifL from Klebsiella pneumoniae exhibits ATP hydrolyzing activity only when synthesized under nitrogen sufficiency.
abstract: The inhibitory function of Klebsiella pneumoniae NifL on NifA transcriptional activity in vitro is stimulated by ATP and ADP when NifL is synthesized under nitrogen sufficiency (NifL(NH4)). Further characterizations showed that NifL(NH4) binds and hydrolyzes ATP (2500 mU/mg). Analyzing fusions between MalE and different portions of NifL, we localized both the ATP binding site and ATP hydrolysis activity to the N-terminal domain of NifL. In contrast, NifL synthesized under nitrogen limitation is not affected by adenine nucleotides and exhibits no ATP hydrolyzing activity. These major differences indicate that the stimulation of the inhibitory function of NifL and the ability to hydrolyze ATP depend on a specific NifL conformation induced by ammonium. We hypothesize that the presence of ammonium alters the conformation of NifL, enabling it to use the energy of ATP hydrolysis to increase the efficiency of NifL-NifA complex formation.
authors.affiliation: Institut für Mikrobiologie und Genetik, Universität Göttingen, Grisebachstrasse 8, 37077 Göttingen, Germany.
authors.forename: Kai
authors.initials: K
authors.lastname: Klopprogge
authors.forename: Jessica
authors.initials: J
authors.lastname: Stips
authors.forename: Ruth A
authors.initials: RA
authors.lastname: Schmitz
mesh_terms: D017766:Acid Anhydride Hydrolases / Q000378:metabolism; D000244:Adenosine Diphosphate / Q000494:pharmacology; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D001665:Binding Sites; D006868:Hydrolysis / Q000187:drug effects; D007711:Klebsiella pneumoniae / Q000737:chemistry / Q000378:metabolism*; D009584:Nitrogen / Q000737:chemistry; D043583:Nucleoside-Triphosphatase; D011487:Protein Conformation; D000644:Quaternary Ammonium Compounds; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; C061338:NifA protein, Bacteria; D000644:Quaternary Ammonium Compounds; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C084296:nifL protein, Bacteria; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D017766:Acid Anhydride Hydrolases; D000251:Adenosine Triphosphatases; D043583:Nucleoside-Triphosphatase; D009584:Nitrogen