The F 1-ATPase or BF 1 factor was purified from Micrococcus lysodeikticus substrain B grown in a synthetic medium in the presence of tritiated amino acids. When analyzed in sodium dodecyl sulfate-7% polyacrylamide gels, the fresh purified preparation contained α, β, γ subunits (referred as the intrinsic subunits) and two other polypeptides (designated as X and component of relative mobility 1.0) whose status as subunits remains to be established. This overall polypeptide composition was similar to that of the F 1-ATPase isolated from the same strain grown in complex medium (J. Carreira, J. M. Andreu, M. Nieto, and E. Muñoz., 1976 Mol. Cell. Biochem. 10, 67–76). The distribution of 3H-labeled amino acids into purified F 1-ATPase and its constituent polypeptides under different stages of growth was used to investigate the biosynthetic relationship between the different polypeptides. The incorporation of amino acids into purified BF 1 factor was slower than that of cytoplasmic and other membrane proteins. In isotope-dilution and chase experiments, F 1-ATPase showed one of the slowest rates of decay of the incorporated label. These results point out that F 1-ATPase of M. lysodeikticus undergoes slower turnover than the overall cytoplasmic and membrane proteins. Pulse and chase experiments allowed us to conclude that the α, β, γ subunits and the components of relative mobility 1.0 are independent with differences in their turnover and therefore do not bear any apparent relation as precursors-products. The two major subunits represent seemingly the “core” of ATPase, the β subunit behaving like the most stable component. On the other hand, the γ subunit appears to be synthesized independently from this α + β complex.