The composition and the structure of bacterioferritin of Escherichia coli

Abstract

Bacterioferritin isolated from Escherichia coli is of two kinds: a protein containing a polynuclear iron compound, the bacterioferritin proper and a protein free of the polynuclear iron compound, the apo-bacterioferritin. Bacterioferritin of both kinds is characterized by absorption maxima at 417,530 and 560 nm, contributed by protohaem IX. Single crystals of bacterioferritin of the space group I432 suggest that the molecule is made up of 24 identical subunits related by a cubic point symmetry. The molecular weight of the protein subunit, as determined by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, is 15000. In the electron microscope the bacterioferritin molecule appears to be a sphere of 9.5 nm (95 A) diameter composed of a negatively staining outer shell and an inner electron-dense core of 6 nm (60 A) diameter.

A comparison of the magnetic properties of polysaccharide iron complex (PIC) and ferritin

“…In region (2) (H < 5 kOe, T> TB) we noted that the magnetization becomes a simple sum of two con tributions as long as the thermal energy exceeds both magnetic energies. Hence the initial 'total' susceptibility XOT in this region becomes a simple sum of two susceptibilities; a superparamagnetic Xp susceptibility and an antiferromagnetic XA susceptibility, (11) In region (4) (H> 20 kOe, T ~ TB)' the super paramagnetic magnetization will saturate, as we have seen in Section 3. netic moment of Fe3+ is 5.92 J.LB' Blaise et al [5,6] has reported a value of ,.., 5.08 JLB for simi lar mammalian ferritin. The difference in these values may be due to the higher density and order of PIC which may increase the number of antiferromagnetic interactions between the atoms, i.e.…”

“…Ferritin is an ubiquitous protein, widespread among plants, animals, and in several bacteria, that is designed to store and maintain iron in an available, non-toxic form [11][12][13]. In every case, the molecule consists of a hydrous ferric oxide core sequestered in a roughly spheroidal, 120 A diameter protein shell.…”

Cloning and sequencing of the bacterioferritin gene of Brucella melitensis 16M strain

“…Six of the seven N-terminal residues of this protein are identical to six of the seven Nterminal residues of Nitrobacter winogradskyi bacterioferritin (BFR) [7] and five are identical to five of the seven N-terminal residues of Escherichia coli BFR [8]. BFR is an iron storage haemoprotein composed of 24 subunits assembled into a spherical protein shell containing approximately 12 haems per 24 subunits [9][10][11] and has been detected in many species [12][13][14][15][16].…”

Perspectives for Photobiology in Molecular Solar Fuels

“…[79] First identified from its optical spectrum as cytochrome b 1 in 1934 by Keilin, [80] BFR is a soluble non-toxic iron storage and detoxification protein. [81,82] The expressed protein assembles into a hollow, almost spherical shell-like nanostructure (,8 nm internal diameter) of 24 subunits configured as a dodecameric structure (Fig. 3a).…”