Iron core mineralisation in prokaryotic ferritins.
BACKGROUND
To satisfy their requirement for iron while at the same time countering the toxicity of this highly reactive metal ion, prokaryotes have evolved proteins belonging to two distinct sub-families of the ferritin family: the bacterioferritins (BFRs) and the bacterial ferritins (Ftns). Recently, Ftn homologues have also been identified and characterised in archaeon species. All of these prokaryotic ferritins function by solubilising and storing large amounts of iron in the form of a safe but bio-available mineral.


METHODS
The mechanism(s) by which the iron mineral is formed by these proteins is the subject of much current interest. Here we review the available information on these proteins, with particular emphasis on significant advances resulting from recent structural, spectroscopic and kinetic studies.


CONCLUSIONS
Current understanding indicates that at least two distinct mechanisms are in operation in prokaryotic ferritins. In one, the ferroxidase centre acts as a true catalytic centre in driving Fe(2+) oxidation in the cavity; in the other, the centre acts as a gated iron pore by oxidising Fe(2+) and transferring the resulting Fe(3+) into the central cavity.


CONCLUSIONS
The prokaryotic ferritins exhibit a wide variation in mechanisms of iron core mineralisation. The basis of these differences lies, at least in part, in structural differences at and around the catalytic centre. However, it appears that more subtle differences must also be important in controlling the iron chemistry of these remarkable proteins.
Le Brun
Nick E
NE
Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, UK. n.le-brun@uea.ac.uk
Crow
Allister
A
Murphy
Michael E P
ME
Mauk
A Grant
AG
Moore
Geoffrey R
GR
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D020134:Catalytic Domain; D005290:Ferric Compounds / Q000737:chemistry / Q000378:metabolism; D005293:Ferritins / Q000737:chemistry* / Q000378:metabolism*; D007501:Iron / Q000737:chemistry / Q000378:metabolism*; D008903:Minerals / Q000737:chemistry / Q000378:metabolism; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011387:Prokaryotic Cells / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; D005290:Ferric Compounds; D008903:Minerals; D005293:Ferritins; D007501:Iron