Early formation of intracytoplasmic membranes in Rhodospillum rubrum.

Cytoplasmic and intracytoplasmic membranes were isolated from Rhodospirillum rubrum by equilibrium sucrose density gradient centrifugation. Immediately after the induction of photosynthetically active intracytoplasmic membranes, bacteriochlorophyll is incorporated predominantly into the cytoplasmic membrane. With increasing pigment concentrations the newly arising intracytoplasmic membranes become sites of preferential bacteriochlorophyll incorporation. During this process the infrared absorption band of the pigment shows a red shift. The shift is more pronounced with intracytoplasmic than with cytoplasmic membranes. Pulse-chase of cytoplasmic membrane proteins reveals that such proteins become constituents of intracytoplasmic membranes.