Immunological and fluorescence studies with the coupling factor ATPase from Rhodospirillum rubrum

1. Purification of the coupling factor ATPase from Rhodospirillum rubrum has been achieved by a combination of a previously described procedure with chromatography on DEAE-Sephadex A50. 2. Identification of the coupling factor ATPase during purification, and estimation of the relative amount of the enzyme in each fraction was greatly simplified by utilization of its unusual fluorescence. 3. Preparations of R. rubrum coupling factor ATPase injected into rabbits yielded antisera which were suitable for following the course of purification. 4. Judged by immunoelectrophoretic analysis and polyacrylamide gel electrophoresis the final preparation was pure. Under standardized conditions, apparently pure preparations showed fluorescence ratios at 300/350 nm of 3-6, which are considerably higher than those reported for pure CF1 from chloroplasts. 5. The enzyme lost its activity and changed its immunological identity during prolonged storage and by treatment with urea. Antisera against urea-treated enzyme showed the presence of two distinct antigens in the modified preparations.