A coupling factor in bacterial photophosphorylation.

The photophosphorylation activity of pigmented particles derived from membranes of the photosynthetic bacterium Rhodopseudomonas caflsulata is greatly diminished by sonic treatment in the presence of EDTA. Activity can be largely restored to treated particles by addition of solubilized protein factor or factors, which functionally resemble coupling factors isolated from other kinds of energy-converting systems. Evidence is presented in support of the conclusion that the R. capsulata factor is required for coupling phosphorylation to electron transport rather than for catalyzing electron transport.