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The Structure of the BfrB–Bfd Complex Reveals Protein–Protein Interactions Enabling Iron Release from Bacterioferritin
journal contribution
posted on 2016-01-07, 20:50 authored by Huili Yao, Yan Wang, Scott Lovell, Ritesh Kumar, Anatoly
M. Ruvinsky, Kevin P. Battaile, Ilya A. Vakser, Mario RiveraFerritin-like molecules are unique to cellular iron homeostasis
because they can store iron at concentrations much higher than those
dictated by the solubility of Fe3+. Very little is known
about the protein interactions that deliver iron for storage or promote
the mobilization of stored iron from ferritin-like molecules. Here,
we report the X-ray crystal structure of Pseudomonas
aeruginosa bacterioferritin (Pa-BfrB)
in complex with bacterioferritin-associated ferredoxin (Pa-Bfd) at 2.0 Å resolution. As the first example of a ferritin-like
molecule in complex with a cognate partner, the structure provides
unprecedented insight into the complementary interface that enables
the [2Fe-2S] cluster of Pa-Bfd to promote heme-mediated
electron transfer through the BfrB protein dielectric (∼18
Å), a process that is necessary to reduce the core ferric mineral
and facilitate mobilization of Fe2+. The Pa-BfrB–Bfd complex also revealed the first structure of a Bfd,
thus providing a first view to what appears to be a versatile metal
binding domain ubiquitous to the large Fer2_BFD family of proteins
and enzymes with diverse functions. Residues at the Pa-BfrB–Bfd interface are highly conserved in Bfr and Bfd sequences
from a number of pathogenic bacteria, suggesting that the specific
recognition between Pa-BfrB and Pa-Bfd is of widespread significance to the understanding of bacterial
iron homeostasis.