Bacfer iron cores

Pseudomonas aerogenes ferredoxin, 33 55-56 Pseudomonas aeruginosa bacfer iron cores, 36 452 diheme cytochrome c peroxidase, 36 242-245... 

The EPR and electronic spectra of the heme of bacfer are not significantly affected by the presence of the nonheme iron core (30, 73). Thus the redox potential difference of the heme iron in apo- and holobacfer (145) (Table II) is most probably caused by a long-range electrostatic effect of the core charge. This indicates that the core carries an overall... 

Some of the characteristics of the nonheme iron cores of ferritins and hacfers are given in Table II. As can be seen there is a wide variation in properties, though these do not seem to depend solely on overall core size. The mean core diameters measured by electron microscopy for human ferritin (84) and P. aeruginosa hacfer (100) were found to he 70-75 and 60-65 A, respectively, with, in both cases, a distribution of sizes between 55 and 80 or 85 A. The maximum core attainable for human or horse ferritin corresponds to 4500 atoms of Fe per molecule (49), or —33% of the mass of the fully loaded protein. The bacfer core contains less iron and thus is considerably less densely packed. 

Interestingly, the difference in redox potential between the heme of apobacfer and the core of holobacfer is —250 mV 145), which is comparable to the difference in redox potential between cytochrome 65 and the core of ferritin of —190 mV. It may he in both cases that the heme accepts electrons from the growing core when the incoming Fe + is oxidized to Fe +. If this is so, the marked reduction in the redox potential of the heme of bacfer once the core is partially loaded could act as a control to ensure that some of the core iron remained in the Fe state, or even to limit the growth of the core. 

---