Protein-protein Interactions Regulate the Release of Iron Stored in Bacterioferritin

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© 2016 John Wiley & Sons, Inc. All rights reserved. Iron storage proteins, ferritin (Ftn) and bacterioferritin (Bfr), are dynamic regulators of iron levels in bacteria. Ftn and Bfr appear to be essential for the survival and virulence of pathogens in a host, suggesting that these molecules may be good targets for the development of new antibiotics. Despite their importance in iron metabolism, little is known about the protein-protein interactions that regulate iron delivery for storage in Ftn or Bfr, or the mobilization of stored iron for incorporation in metabolism. This chapter reviews recent findings demonstrating that mobilization of iron stored in Bfr requires binding of Bfd (bacterioferritin-associated ferredoxin), which enables heme-mediated electron transfer from the [2Fe-2S] cluster in Bfd to the Fe3+ mineral stored in Bfr, for subsequent mobilization of Fe2+. The crystal structure of the BfrB-Bfd complex, which reveals unprecedented molecular information, is in agreement with the model of Fe2+ mobilization derived from biochemical studies. The structure of the complex also showed that residues from both proteins, which participate at the complex interface, are conserved in equivalent proteins from several pathogens, indicating that the BfrB-Bfd interaction is of widespread significance in bacterial iron homeostasis.

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Stress and Environmental Regulation of Gene Expression and Adaptation in Bacteria

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