Structural diversity of polyoxomolybdate clusters along the three-fold axis of the molybdenum storage protein

作者：Poppe Juliane; Warkentin Eberhard; Demmer Ulrike; Kowalewski Bjoern; Dierks Thomas; Schneider Klaus^*; Ermler Ulrich

来源：Journal of Inorganic Biochemistry, 2014, 138: 122-128.

DOI：10.1016/j.jinorgbio.2014.05.009

• Azotobacter vinelandii
• Molybdenum storage protein
• Polyoxometalate
• Template
• Crystal structure

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 angstrom resolution. In contrast to the Mo alpha-out binding site occupied by an Mo-3 cluster, the Mo alpha-in and Mo-beta 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 %26quot;Mo alpha-in cluster ensemble%26quot; was interpreted as an antiprism-like Mo-6 species superimposed with an Mo-7 pyramide and the %26quot;Mo-beta cluster ensemble%26quot; as an Mo-13 cluster (present mostly ins degraded form) composed of a pyramidal Mo-7 and a Mo-3 building block linked by three spatially separated MoOx units. Inside the ball-shaped Mo-13 cluster sits an occluded central atom, perhaps a metal ion. POM cluster formation at the Mo alpha-in, and Mo-beta sites appears to be driven by filtering out and binding/protecting self-assembled transient species complementary to the protein template.

• 出版日期2014-9