An acid-stable cytochrome in iron-oxidizingLeptospirillum ferrooxidans

A novel, apparently acid-stable cytochrome has been purified from Leptospirillum ferrooxidans in which it probably functions in the ‘downhill’ transfer of electrons from ferrous iron. It appeared to comprise a single polypeptide of apparent Mr 17.9 kDa as determined by SDS-PAGE. Non-denaturing PAGE showed this to be the approximate size of the native protein. The oxidized cytochrome showed a broad absorption maximum at 422 nm and was readily reduced with dithionite or ferrous iron to give a form with absorption maxima at 440 and 579 nm. A mid-point potential of +680 mV at pH 3.5 was determined. Iron and zinc were found at concentrations approaching one atom of each per cytochrome molecule.