Nature Structural Biology pp 297 - 302

Like humans, many bacteria need to obtain essential iron from the environment. But unlike humans, these microorganisms have to take the metal in the forms in which Nature provides it, often as insoluble minerals. A paper in the March issue of Nature Structural Biology now provides the first view of the interface between a bacterial iron-binding protein and clusters of metal ions that resemble the mineral forms existing in the environment. The findings suggest a mechanism for the initial stages of iron uptake by bacteria.

Peter Sadler and colleagues (University of Edinburgh, UK) have determined the crystal structure of the bacterial iron-binding protein bound to multiple hafnium ions. Hafnium has some properties similar to iron and is often found in the same geological minerals with iron. The crystal structure reveals that the hafnium ions are organized in a cluster 'bridged' by oxygen atoms. In addition, the architecture of the metal cluster bound to the protein resembles the structure of the hafnium oxide mineral. This is the first structure of the iron-binding protein bound to mineral-like metal clusters. Together with other features described in the research paper, the structure suggests how bacteria may acquire iron from minerals under iron-limited conditions.