Variations of NADH oxidase activity and bacteriochlorophyll contents during membrane differentiation in Rhodospirillum rubrum

Abstract

1. 1. Alterations in the protein patterns depending on culture conditions were investigated in purified thylakoids isolated from Rhodospirillum rubrum. The corresponding bacteriochlorophyll contents and NADH oxidase activities of the thylakoids were determined. 2. 2. High oxygen tension both in light and in darkness caused preferential synthesis of specific membrane proteins. These proteins are representative of cytoplasmic membrane fractions from anaerobically light-grown and aerobically dark-grown cells. Under these conditions the bacteriochlorophyll contents of thylakoids decreased whereas the activity of NADH oxidase increased 4–5-fold. 3. 3. When such cells were incubated anaerobically at low light intensity (400 lux), proteins were newly synthesized that were typical of thylakoids from anaerobic illuminated cells. These proteins had not been formed previously in the presence of oxygen. The amount of bacteriochlophyll increased. However, NADH oxidase activity on a bacteriochlorophyll basis decreased. 4. 4. In cultures growing anerobically at moderate light intensity (400 lux) all of the thylakoid proteins were synthesized in typical ratios. There was only a very slight increase of NADH oxidase activity. Bacteriochlorophyll contents remained nearly constant. 5. 5. The results strongly suggest a correlation between variations in catalytic functions and protein patterns of thylakoids.