Abstract
The reaction centers of heliobacteria belong to a Fe-S type, like those of green sulfur bacteria and PSΙ. Four Ferredoxins, Fd A, Fd B, Fd C, and Fd D, were extracted from heliobacterium Heliophilum fasciatum cells, and purified by ammonium sulfate fractionation, anion-exchange chromatography and hydrophobic interaction chromatography chromatographies under strictly anaerobic conditions. The absorption spectra of the purified Fds were typical of those of the 2[4Fe-4S] cluster type Fds, with absorption peaks at about 385 and 285 nm and with a shoulder at about 300 nm. Cryogenic EPR measurements showed that the purified Fds were dithionite reducible at pH8.0 and those spectral features were typical 4Fe-4S type iron-sulfur cluster. Although A385/A280 ratio of Fd B and Fd C were not changed significantly up to 24h under the air at 4°C, those of Fd A and Fd D were decrease by 50% and 20% respectively.
