Preliminary characterization of the membrane-bound adenosine triphosphatase of Azotobacter vinelandii

The membrane-bound adenosine triphosphatase (ATPase) of Azotobacter vinelandii was examined and its direct relationship to the Azotobacter electron transport fraction (R3) was established readily. Sonically disrupted Azotobacter cells were differentially centrifuged and distribution of ATPase activity was examined in particulate and soluble fractions. Highest specific activity for ATPase was consistently found in the R3 fraction, a particulate fraction which sediments on ultracentrifugation at 144,000 x g for 2 hr. By increasing the interval time of sonication, the membrane-bound ATPase activity could not be solubilized nor released into the supernatant fraction. [...]