Genetic evidence for the role of isocytochrome c2 in photosynthetic growth of Rhodobacter sphaeroides Spd mutants

Rhodobacter sphaeroides Spd mutants accumulates a novel form of cytochrome c2, isocytochrome c2 (isocyt c2), which allows them to suppress the photosynthetic deficiency of cyt c2 mutations. The gene coding for isocyt c2, (cycI) was cloned, sequenced and physically mapped. Genetic analysis of cycI showed that it is necessary and sufficient for cyt c2-independent photosynthetic growth.