title: Structure of GlnK1, a signalling protein from Archaeoglobus fulgidus.
abstract: GlnB and GlnK are ancient signalling proteins that play a crucial role in the regulation of nitrogen assimilation. Both protein types can be present in the same genome as either single or multiple copies. However, the gene product of glnK is always found in an operon together with an amt gene encoding an ammonium-transport (Amt) protein. Complex formation between GlnK and Amt blocks ammonium uptake and depends on the nitrogen level in the cell, which is regulated through the binding of specific effector molecules to GlnK. In particular, an ammonium shock to a cell culture previously starved in this nitrogen source or the binding of ATP to purified GlnK can stimulate effective complex formation. While the binding of ATP/ADP and 2-oxoglutarate (as a signal for low intracellular nitrogen) to GlnK have been reported and several GlnB/K protein structures are available, essential functional questions remain unanswered. Here, the crystal structure of A. fulgidus GlnK1 at 2.28 Å resolution and a comparison with the crystal structures of other GlnK proteins, in particular with that of its paralogue GlnK2 from the same organism, is reported.
authors.affiliation: Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Litz
authors.forename: Sarah
authors.initials: S
authors.lastname: Helfmann
authors.forename: Stefan
authors.initials: S
authors.lastname: Gerhardt
authors.forename: Susana L A
authors.initials: SL
authors.lastname: Andrade
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019611:Archaeoglobus fulgidus / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D018360:Crystallography, X-Ray / Q000379:methods; D004926:Escherichia coli / Q000235:genetics; D007656:Ketoglutaric Acids / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009584:Nitrogen / Q000378:metabolism; D009876:Operon; D051922:PII Nitrogen Regulatory Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D015203:Reproducibility of Results; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000235:genetics*; D014961:X-Ray Diffraction
chemical_list: D019843:Archaeal Proteins; D002352:Carrier Proteins; D007656:Ketoglutaric Acids; D051922:PII Nitrogen Regulatory Proteins; D011994:Recombinant Proteins; D009584:Nitrogen