COUPLING FACTOR ATPASE COMPLEX OF RHODOSPIRILLUM-RUBRUM PURIFICATION AND CHARACTERIZATION OF AN OLIGOMYCIN AND N,N'-DICYCLOHEXYLCARBODIIMIDE-SENSITIVE (CA2+ + MG2+)-ATPASE

An ATPase complex sensitive to the energy transfer inhibitors oligomycin, dicyclohexylcarbodiimide and venturicidin has been solubilized from Rhodospirillum rubrum chromatophores with Triton X-100 and further purified by centrifugation on a glycerol gradient. The partially purified RrF0 · F1 contains 13 distinct polypeptide subunits, as revealed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, including the subunits of the oligomycin-insensitive, water-soluble RrF1 ATPase. The ATPase activity of RrF0 · F1 as that of the membrane-bound enzyme complex depends on Ca2+ or Mg2+ and from detailed kinetic studies it is concluded that the divalent cation-ATP complex is the substrate for both ATPase complexes. Free ATP and free Mg2+ act as competitive inhibitors, with Ki values of 1 mM and 7 μM, respectively. The subunit composition of the purified RrF0 · F1 and its similarity to the membrane-bound ATPase with respect to cation dependence and sensitivity to energy transfer inhibitors suggests that it contains all the subunits of the R. rubrum coupling factor-ATPase complex. © 1979.