Photosynthetic Electron Transport Chain of Chlamydomonas reinhardi. V. Purification and Properties of Cytochrome 553 and Ferredoxin

Abstract

Cytochrome 553 and ferredoxin were isolated and purified from acetone powders prepared from intact cells of the wild-type strain of Chlamydomonas reinhardi. Purification was achieved by ion exchange chromatography on DEAE cellulose and gel filtration on Sephadex G-75.Cytochrome 553 could be oxidized with postassium ferricyanide and reduced with sodium ascorbate. The absorption maxima of the cytochrome in reduced form were found to be alpha-band 552.5 nm, beta-band 522.5 nm, and Soret band 416.5 nm. The normal redox potential was +0.37 volt, and the molecular weight was estimated to be 12,000 +/- 2000. The cytochrome closely resembled that of the c-type cytochromes extracted from Euglena and Porphyra. When cultures were harvested after they had entered stationary phase, the cytochrome could be extracted in soluble form, and in some cases a yield of one cytochrome per 1000 chlorophyll molecules could be obtained.Ferredoxin showed absorption maxima at 278, 330, 420 and 460 nm. Thus it resembles the ferredoxin extracted from spinach. The molecular weight of the ferredoxin was estimated to be 15,000 +/- 2000.