Purification and Properties of Monomeric Cytochrome f from Charlock, Sinapis arvensis L.

Abstract

Monomeric cytochrome f was purified to homogeneity, as judged by polyacrylamide gel electrophoresis, isoelectric focusing and analytical ultracentrifugation, from the leaves of charlock, S. arvensis L. The cytochrome was obtained in an aqueous extract following extraction of leaf lipids with butan-2-one, and was subsequently purified by acetone precipitation and chromatography on DEAE-cellulose, Sephadex G-100 and hydroxylapatite. The purified cytochrome had absorbance ratios of A422/A280 = 7.3 and A554/A280 = 1.07 in the reduced form. There was no indication of the presence of an absorbance band at 695 nm in the oxidized form. The cytochrome had a midpoint redox potential of +365 mV and was oxidized very rapidly by parsley [Petroselinum crispum] plastocyanin. The MW of the cytochrome was approximately 27,000 as determined by sedimentation equilibrium and by polyacrylamide gel electrophoresis in the presence of dodecylsulfate. The sedimentation coefficient .**GRAPHIC**. of cytochrome f was 2.48 S. The cytochrome had an isoelectric point at pH 5.50 determined by isoelectric focusing in polyacrylamide gels.