title: A new type of metalloprotein: The Mo storage protein from azotobacter vinelandii contains a polynuclear molybdenum-oxide cluster.
abstract: Azotobacter vinelandii is a diazotrophic bacterium characterized by the outstanding capability of storing Mo in a special storage protein, which guarantees Mo-dependent nitrogen fixation even under growth conditions of extreme Mo starvation. The Mo storage protein is constitutively synthesized with respect to the nitrogen source and is regulated by molybdenum at an extremely low concentration level (0-50 nM). This protein was isolated as an alpha4beta4 octamer with a total molecular mass of about 240 kg mol(-1) and its shape was determined by small-angle X-ray scattering. The genes of the alpha and beta subunits were unequivocally identified; the amino acid sequences thereby determined reveal that the Mo storage protein is not related to any other known molybdoprotein. Each protein molecule can store at least 90 Mo atoms. Extended X-ray absorption fine-structure spectroscopy identified a metal-oxygen cluster bound to the Mo storage protein. The binding of Mo (biosynthesis and incorporation of the cluster) is dependent on adenosine triphosphate (ATP); Mo release is ATP-independent but pH-regulated, occurring only above pH 7.1. This Mo storage protein is the only known noniron metal storage system in the biosphere containing a metal-oxygen cluster.
authors.affiliation: Lehrstuhl für Anorganische Chemie I, Universität Bielefeld, Universitätsstrasse 25, 33615 Bielefeld, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Fenske
authors.forename: Manuel
authors.initials: M
authors.lastname: Gnida
authors.forename: Klaus
authors.initials: K
authors.lastname: Schneider
authors.forename: Wolfram
authors.initials: W
authors.lastname: Meyer-Klaucke
authors.forename: Jörg
authors.initials: J
authors.lastname: Schemberg
authors.forename: Volker
authors.initials: V
authors.lastname: Henschel
authors.forename: Anne-Katrin
authors.initials: AK
authors.lastname: Meyer
authors.forename: Arndt
authors.initials: A
authors.lastname: Knöchel
authors.forename: Achim
authors.initials: A
authors.lastname: Müller
mesh_terms: D000595:Amino Acid Sequence; D016948:Azotobacter vinelandii / Q000737:chemistry* / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008667:Metalloproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D008982:Molybdenum / Q000737:chemistry / Q000378:metabolism*; D010087:Oxides / Q000737:chemistry*; D011485:Protein Binding; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D001426:Bacterial Proteins; D008667:Metalloproteins; D010087:Oxides; D021122:Protein Subunits; D008982:Molybdenum