[Isolation and characterization of rubredoxin from Acinetobacter calcoaceticus]

Acinetobacter calcoaceticus growing on long-chain n-alkanes contains a soluble iron-sulfur protein, which corresponds in its properties to a rubredoxin. It was prepared from the 50000 X g supernatant of ultrasonically treated cells using ion exchange chromatography on DEAE cellulose and gel filtration on Sephadex G-75. The isolated protein is pure electrophoretically, but yields two bands corresponding to molecular weights of 6000 and 12000 respectively. A content of 11 acidic against 6 basic amino acids is in line with the acidic character of the protein. The absence of acid-labile sulfur, content of 4 cysteine residues and one iron atom per polypeptide chain and the typical absorption maxima at gamma = 280, 380, and 490 nm exclude the presence of a ferredoxin. Involvement of the rubredoxin in the alkane hydroxylation is discussed.