The binding of haem and zinc in the 1.9 A X-ray structure of Escherichia coli bacterioferritin.

addresses: School of Biosciences, Henry Wellcome Building for Biocatalysis, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK.types: Journal Article; Research Support, Non-U.S. Gov'tThis a post-print, author-produced version of an article accepted for publication in Journal of Biological Inorganic Chemistry . Copyright © 2008 Springer Verlag / SBIC . The definitive version is available at http://link.springer.com/article/10.1007%2Fs00775-008-0438-8The crystal structure of Escherichia coli bacterioferritin has been solved to 1.9 A, and shows the symmetrical binding of a haem molecule on the local twofold axis between subunits and a pair of metal atoms bound to each subunit at the ferroxidase centre. These metals have been identified as zinc by the analysis of the structure and X-ray data and confirmed by microfocused proton-induced X-ray emission experiments. For the first time the haem has been shown to be linked to both the internal and the external environments via a cluster of waters positioned above the haem molecule