PURIFICATION AND PROPERTIES OF A LOW-REDOX-POTENTIAL TETRAHEME CYTOCHROME C(3) FROM SHEWANELLA-PUTREFACIENS

Shewanella putrefaciens is a facultatively anaerobic bacterium in the gamma group of the proteobacteria, capable of utilizing a,vide variety of anaerobic electron accepters. An examination of its cytochrome con tent revealed the presence of a tetraheme, low-redox-potential (E(o) = -233 mV), cytochrome c-type cytochrome with a molecular mass of 12,12 0 Da and a pI of 5.8. The electron spin resonance data indicate a bis- histidine coordination of heme groups. Reduction of ferric citrate was accompanied by oxidation of the cytochrome. The biochemical propertie s suggested that this protein was in the cytochrome c(3) group, which is supported by N-terminal sequence data up to the first heme binding site.