Sulfide induction of synthesis of a periplasmic protein in the cyanobacterium Oscillatoria limnetica.

Two proteins which may play a role in the induction of anoxygenic photosynthesis in Oscillatoria limnetica have been demonstrated by comparing the pattern of labeling during pulses of 35S]methionine of cells incubated under inducing conditions anaerobic conditions plus 3-(3,4-dichlorophenyl)-1,1-dimethylurea, light, and sulfide) with that of cells incubated under noninducing conditions (without sulfide). The major inducible protein has an apparent molecular mass of 11.5 kilodaltons and is associated with a less strongly labeled 12.5-kilodalton protein. The synthesis of both proteins commences within the first 30 min of induction and continues throughout the 2-h induction period. Since these proteins are not synthesized in the presence of dithionite without sulfide, low redox potential alone is insufficient as an inducer of these proteins. Lysozyme treatment and/or osmotic shock of intact cells results in the release of the sulfide-induced proteins. Our data thus indicate that these proteins are located in the periplasmic space of the cells.