37] Cytochrome [formula omitted] complex in cyanobacteria: Common components of respiratory and photosynthetic electron transport systems

Abstract

Publisher Summary This chapter focuses on the common components of respiratory and photosynthetic electron transport systems for cytochrome b6/f complex in cyanobacteria. The cytochrome b6/f complex functions as a plastoquinol-plastocyanin (cytochrome c) reductase under conditions of photosynthetic electron transport. Recent results have also suggested the same complex functions in the cyanobacterial respiratory chain, utilizing reduced pyridine nucleotides as electron donors instead of water. The cytochrome b6/f complex from higher plants has been isolated and extensively characterized, and, although the purification and analysis of the cyanobacterial complex is not as complete, the procedures used for the isolation of the higher plant cytochrome complex are generally applicable to the membranes of cyanobacteria. The procedure described for the isolation of the cytochrome b6/f complex from cyanobacterial membranes is based on one originally developed for membranes from higher plants. The isolation involves treatment of thylakoid membranes to remove extrinsic proteins, solubilization of the cytochrome complex with detergent, and purification of the complex by ammonium sulfate fractionation and sucrose density gradient centrifugation.