title: Structural insights into HypB, a GTP-binding protein that regulates metal binding.
abstract: HypB is a prokaryotic metal-binding guanine nucleotide-binding protein that is essential for nickel incorporation into hydrogenases. Here we solved the x-ray structure of HypB from Methanocaldococcus jannaschii. It shows that the G-domain has a different topology than the Ras-like proteins and belongs to the SIMIBI (after Signal Recognition Particle, MinD and BioD) class of NTP-binding proteins. We show that HypB undergoes nucleotide-dependent dimerization, which is apparently a common feature of SIMIBI class G-proteins. The nucleotides are located in the dimer interface and are contacted by both subunits. The active site features residues from both subunits arguing that hydrolysis also requires dimerization. Two metal-binding sites are found, one of which is dependent on the state of bound nucleotide. A totally conserved ENV/IGNLV/ICP motif in switch II relays the nucleotide binding with the metal ionbinding site. The homology with NifH, the Fe protein subunit of nitrogenase, suggests a mechanistic model for the switch-dependent incorporation of a metal ion into hydrogenases.
authors.affiliation: Max-Planck-Institut für Molekulare Physiologie, Abteilung Strukturelle Biologie, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany.
authors.forename: Raphael
authors.initials: R
authors.lastname: Gasper
authors.forename: Andrea
authors.initials: A
authors.lastname: Scrima
authors.forename: Alfred
authors.initials: A
authors.lastname: Wittinghofer
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000502:physiology*; D001665:Binding Sites; D002845:Chromatography; D018360:Crystallography, X-Ray; D019281:Dimerization; D019204:GTP-Binding Proteins / Q000737:chemistry* / Q000502:physiology*; D006160:Guanosine Triphosphate / Q000737:chemistry*; D008670:Metals / Q000737:chemistry; D017017:Methanococcus / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; C089637:HypB protein, bacteria; D008670:Metals; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins