title: Structural diversity of polyoxomolybdate clusters along the three-fold axis of the molybdenum storage protein.
abstract: The molybdenum storage protein (MoSto) can store more than 100 Mo or W atoms as discrete polyoxometalate (POM) clusters. Here, we describe the three POM cluster sites along the threefold axis of the protein complex based on four X-ray structures with slightly different polyoxomolybdate compositions between 1.35 and 2 Å resolution. In contrast to the Moα-out binding site occupied by an Mo3 cluster, the Moα-in and Moβ binding sites contain rather weak and non-uniform electron density for the Mo atoms (but clearly identifiable by anomalous data), suggesting the presence of POM cluster ensembles and/or degradation products of larger aggregates. The "Moα-in cluster ensemble" was interpreted as an antiprism-like Mo6 species superimposed with an Mo7 pyramide and the "Moβ cluster ensemble" as an Mo13 cluster (present mostly in a degraded form) composed of a pyramidal Mo7 and a Mo3 building block linked by three spatially separated MoOx units. Inside the ball-shaped Mo13 cluster sits an occluded central atom, perhaps a metal ion. POM cluster formation at the Moα-in and Moβ sites appears to be driven by filtering out and binding/protecting self-assembled transient species complementary to the protein template.
authors.affiliation: Max-Planck-Institut für Biophysik, Max-von-Laue-Straße 3, D-60438 Frankfurt am Main, Germany.
authors.forename: Juliane
authors.initials: J
authors.lastname: Poppe
authors.affiliation: Max-Planck-Institut für Biophysik, Max-von-Laue-Straße 3, D-60438 Frankfurt am Main, Germany.
authors.forename: Eberhard
authors.initials: E
authors.lastname: Warkentin
authors.affiliation: Max-Planck-Institut für Biophysik, Max-von-Laue-Straße 3, D-60438 Frankfurt am Main, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Demmer
authors.affiliation: Biochemie I, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, D-33615 Bielefeld, Germany.
authors.forename: Björn
authors.initials: B
authors.lastname: Kowalewski
authors.affiliation: Biochemie I, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, D-33615 Bielefeld, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Dierks
authors.affiliation: Biochemie I, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, D-33615 Bielefeld, Germany. Electronic address: klaus.schneider1@uni-bielefeld.de.
authors.forename: Klaus
authors.initials: K
authors.lastname: Schneider
authors.affiliation: Max-Planck-Institut für Biophysik, Max-von-Laue-Straße 3, D-60438 Frankfurt am Main, Germany. Electronic address: ulrich.ermler@biophys.mpg.de.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Ermler
mesh_terms: D016948:Azotobacter vinelandii / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry*; D001665:Binding Sites; D008667:Metalloproteins / Q000737:chemistry*; D008982:Molybdenum / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding
chemical_list: D001426:Bacterial Proteins; D008667:Metalloproteins; D008982:Molybdenum
keywords: Azotobacter vinelandii; Crystal structure; Molybdenum storage protein; Polyoxometalate; Template