Bacterioferritin (Bfr) is an oligomeric

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

containing both a binuclear iron centre and haem b. The

tertiary Tertiary ( ) is a widely used but obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start ...

and

quaternary structure Protein quaternary structure is the fourth (and highest) classification level of protein structure. Protein quaternary structure refers to the structure of proteins which are themselves composed of two or more smaller protein chains (also refe ...

of Bfr is very similar to that of

ferritin Ferritin is a universal intracellular protein that stores iron and releases it in a controlled fashion. The protein is produced by almost all living organisms, including archaea, bacteria, algae, higher plants, and animals. It is the primary ' ...

. The physiological functions of BFR, which may be other than just iron uptake, are not clear. Bfr forms a roughly spherical, hollow shell from 24 identical subunits, incorporating 12 haem groups. Iron is stored as a hydrated ferric oxide mineral in its central cavity (about 80 Å diameter). The overall complex has cubic (432) symmetry. Each subunit includes a binuclear metalbinding site (the diiron site) linking together the four major helices of the subunit, which has been identified as the

ferroxidase Ferroxidase also known as Fe(II):oxygen oxidoreductase is an enzyme that catalyzes the oxidization of iron II to iron III: : 4 Fe2+ + 4 H+ + O2 ⇔ 4 Fe3+ + 2H2O Examples Human genes encoding proteins with ferroxidase activity include: * CP ...

active site. Bfr from ''

Pseudomonas aeruginosa ''Pseudomonas aeruginosa'' is a common encapsulated, gram-negative, aerobic–facultatively anaerobic, rod-shaped bacterium that can cause disease in plants and animals, including humans. A species of considerable medical importance, ''P. aerugi ...

'' (''Pa''Bfr), unlike other Bfrs, is found to contain two subunit types, which differ considerably in their amino acid sequences. A similar hetero-assembly is seen in the ferritins of higher eukaryotes. Bfr from ''

Escherichia coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus ''Escher ...

'' (''Ec''Bfr) which naturally shows structural instability and an incomplete self-assembly behavior by populating two oligomerization states has been used as a model for studies on the

self-assembly Self-assembly is a process in which a disordered system of pre-existing components forms an organized structure or pattern as a consequence of specific, local interactions among the components themselves, without external direction. When the ...

of minimal protein nano-cages.

References

Frolow, F., Kalb, A. J. & Yariv, J. (1994). Structure of a Unique Twofold Symmetrical Heme-Binding Site. Nature Structural Biology 1, 453–460. Dautant, A., Meyer, J. B., Yariv, J., Precigoux, G., Sweet, R. M., Kalb, A. J. & Frolow, F. (1998). Structure of a monoclinic crystal form of cytochrome b1 (bacterioferritin) from E-coli.

Acta Crystallographica Section D ''Acta Crystallographica'' is a series of peer-reviewed scientific journals, with articles centred on crystallography, published by the International Union of Crystallography (IUCr). Originally established in 1948 as a single journal called ''Acta ...

-Biological Crystallography 54, 16–24.

External links

* Bacterial enzymes EC 1.16.3 Storage proteins Iron metabolism {{enzyme-stub