Effect of 2,2 '-dipyridyl on accumulation of protoporphyrin IX and its derivatives in yeast mitochondria and plasma membranes

The iron chelator 2,2'-dipyridyl (0.2 mM) more than fourfold increased the concentration of protoporphyrin IX and also of its zinc-containing complex in mitochondria of the yeast Saccharomyces cerevisiae. Protoporphyrin IX an d a chlorine derivative of protoporphyrin IX which fluoresces at 670-675 nm were found in isolated plasma membranes of the yeast grown in the presence of 0.2 mM 2,2'-dipyridyl. The accumulation of endogenous porphyrins result ed in intensification of lipid photoperoxidation in mitochondria and plasma membranes and in a dramatically increased sensitivity of the cells to visi ble light (400-600 nm). The relative contribution of photodestruction of su bcellular structures to photoinduced cell inactivation is discussed.