AN f-TYPE CYTOCHROME FROM CHLORELLA VULGARIS

A method for isolating an f-type cytochrome (Chlorella cytochrome554) from Chlorella vulgaris var. viridis (CHODAT) utilizingN, N-diethylaminoethylcellulose is described. The spectrum ofreduced Chlorella cyt. 554 has absorption maxima at 554 mµ(-band), 524 mµ (ß-band), 417 mµ (SORETband), 352 mµ, 319 mµ and 277 mµ (proteinband). The oxidized form has absorption maxima at 554mµ530 mµ, (ß-band), 412 mµ (SORET band),360mµ 322 mµ and 275 mµ (protein band). Thespectral characteristics resembled other f-type cytochromes,e. g. in the high SORET to -extinction ratio (6.8) and an asymmetric-absorption band (especially at liquid N₂ temperature) ; butcharacteristic differences were present. Mitochondria from whitelupine seedlings and sweet potato roots reduced Chlorella cyt.554. From the effects of antimycin A and 2-heptyl-4-hydroxyquinolineN-oxide it appears that Chlorella cyt. 554 was reduced sequentiallybefore cytochrome a+a₃ and near the level of the cytochromesof the b type. Oxidation was slow using lupine mitochondriaand nil with sweet potato mitochondria. The oxidation-reductionpotential at pH 7.2 and 30? was 0.35 V. Ascorbate, cysteine,glutathione and Na₂S₂O₄ readily reduced Chlorella cyt. 554.The cytochrome was not autoxidizable and was slowly oxidizedby excess potassium ferricyanide. The reduced form did not reactwith CO and was not adsorbed by IRC-50 or Cellex-P cation exchangers. ¹ Temporary address until September 1961: Department of HorticulturalScience, University of California, Los Angeles 24, California,U. S. A.² Present address: Plant Industry Station, Pioneering ResearchLaboratory, Marketing Quality Research Division, AgriculturalMarketing Service, Beltsville, Maryland, U. S. A. (Received January 16, 1961; )