4IXK

Anaerobic crystal structure of iron soaked (2 h) ferritin from Pseudo-nitzschia multiseries

Summary for 4IXK

• Entry DOI: 10.2210/pdb4ixk/pdb
• Related: 4ISM 4ISP 4ITT 4ITW 4IWJ 4IWK
• Descriptor: Ferritin, FE (III) ION (3 entities in total)
• Functional Keywords: ferritin, 4 helix bundle, iron storage, acetamido-cysteines, transport protein
• Biological source: Pseudo-nitzschia multiseries
• Total number of polymer chains: 8
• Total formula weight: 151382.60

Authors

Pfaffen, S.,Murphy, M.E.P. (deposition date: 2013-01-26, release date: 2013-03-20, Last modification date: 2017-11-15)

Primary citation

Pfaffen, S.,Abdulqadir, R.,Le Brun, N.E.,Murphy, M.E.
Mechanism of ferrous iron binding and oxidation by ferritin from a pennate diatom.
J.Biol.Chem., 288:14917-14925, 2013

PubMed Abstract: A novel ferritin was recently found in Pseudo-nitzschia multiseries (PmFTN), a marine pennate diatom that plays a major role in global primary production and carbon sequestration into the deep ocean. Crystals of recombinant PmFTN were soaked in iron and zinc solutions, and the structures were solved to 1.65-2.2-Å resolution. Three distinct iron binding sites were identified as determined from anomalous dispersion data from aerobically grown ferrous soaked crystals. Sites A and B comprise the conserved ferroxidase active site, and site C forms a pathway leading toward the central cavity where iron storage occurs. In contrast, crystal structures derived from anaerobically grown and ferrous soaked crystals revealed only one ferrous iron in the active site occupying site A. In the presence of dioxygen, zinc is observed bound to all three sites. Iron oxidation experiments using stopped-flow absorbance spectroscopy revealed an extremely rapid phase corresponding to Fe(II) oxidation at the ferroxidase site, which is saturated after adding 48 ferrous iron to apo-PmFTN (two ferrous iron per subunit), and a much slower phase due to iron core formation. These results suggest an ordered stepwise binding of ferrous iron and dioxygen to the ferroxidase site in preparation for catalysis and a partial mobilization of iron from the site following oxidation.

PubMed: 23548912
DOI: 10.1074/jbc.M113.454496

Experimental method

X-RAY DIFFRACTION (2.1 Å)