Genetics of Cytochromes C₂ and BC₁ Complex of Photosynthetic Bacteria

Abstract

Photosynthetic bacteria are endowed with a multitude of b- and c-type cytochromes that are important components of cellular energy transduction pathways operational during the metabolism of various substances¹. They are often soluble and located in the periplasmic space, or are integral membrane proteins spanning the lipid bilayer. Soluble species may also associate, under certain conditions, with various membrane-embedded complexes. The presence or absence of a given set of cytochromes, as well as their relative amounts, although barely studied in many instances, appear well regulated. Different growth conditions induce, or preclude, the synthesis of various cytochromes in function of the cellular needs². Expectedly, the metabolic pathways and the components involved are complex and numerous, but their knowledge is essential for a complete understanding of the biology of the cell. In the past, biochemical studies of cytochromes have been extremely fruitful, allowing the determination of their structural and functional properties^1,2. In more recent years, these studies have also been complemented by molecular biological approaches directed at the analysis of the corresponding DNA structures which contain the information responsible for their structure and their regulated synthesis.