2fl0

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spinqualitylabelsall models 2fl0, resolution 2.70Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Oxidized (All ferric) form of the Azotobacter vinelandii bacterioferritin

Overview

In this work, we report the X-ray crystal structure of the aerobically, isolated (oxidized) and the anaerobic dithionite-reduced (at pH 8.0) forms, of the native Azotobacter vinelandii bacterioferritin to 2.7 and 2.0 A, resolution, respectively. Iron K-edge multiple anomalous dispersion (MAD), experiments unequivocally identified the presence of three independent, iron-containing sites within the protein structure. Specifically, a, dinuclear (ferroxidase) site, a b-type heme site, and the binding of a, single iron atom at the four-fold molecular axis of the protein shell were, observed. In addition to the novel observation of iron at the four-fold, pore, these data also reveal that the oxidized form of the protein has a, symmetrical ferroxidase site containing two five-coordinate iron atoms., Each iron atom is ligated by four carboxylate oxygen atoms and a single, histidyl nitrogen atom. A single water molecule is found within hydrogen, bonding distance of the ferroxidase site that bridges the two iron atoms, on the side opposite the histidine ligands. Chemical reduction of the, protein under anaerobic conditions results in an increase in the average, Fe-Fe distance in the ferroxidase site from approximately 3.5 to, approximately 4.0 A and the loss of one of the ligands, H130. In addition, there is significant movement of the bridging water molecule and several, other amino acid side chains in the vicinity of the ferroxidase site and, along the D helix to the three-fold symmetry axis. In contrast to previous, work, the higher-resolution data for the dithionite-reduced structure, suggest that the heme may be bound in multiple conformations. Taken, together, these data allow a molecular movie of the ferroxidase gating, mechanism to be developed and provide further insight into the iron uptake, and/or release and mineralization mechanism of bacterioferritins in, general.

About this Structure

2FL0 is a Single protein structure of sequence from Azotobacter vinelandii with FE2, MG and HEM as ligands. Full crystallographic information is available from OCA.

Reference

Redox-dependent structural changes in the Azotobacter vinelandii bacterioferritin: new insights into the ferroxidase and iron transport mechanism., Swartz L, Kuchinskas M, Li H, Poulos TL, Lanzilotta WN, Biochemistry. 2006 Apr 11;45(14):4421-8. PMID:16584178

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