Isolation and properties of the complex nonheme-iron-containing cytochrome b557 (bacterioferritin) from Pseudomonas aeruginosa.

A nonheme-iron-containing cytochrome b557, also known as bacterioferritin, was isolated from Pseudomonas aeruginosa. Gel electrophoresis showed that the protein subunits had a molecular weight of 18 kD and it is suggested that the intact molecule contained 24 subunits. The isolated protein contained 8.7% by weight Fe and 8% by weight phosphate. Most of the Fe was contained in the nonheme-iron core and could be readily removed by dialysis against 0.12 M thioglycollic acid. The resulting apobacterioferritin contained approximately one protoporphyrin IX group for every five subunits and, in addition, an unidentified fluorophor. The nonheme-iron core was found to be amorphous with a mean core size of 60-65 A.