THE EPSILON-SUBUNIT AS AN ATPASE INHIBITOR OF THE F1-ATPASE IN ESCHERICHIA-COLI

The isolation of protein ATPAse inhibitor was attempted directly from E. coli membrane extracts to examine the possible presence of a Pullman-Monroy-type inhibitor distinct from the .epsilon. subunit of E. coli ATPase. Purification to homogeneity was achieved in a sequence of steps involving trichloracetic acid precipitation, DEAE-cellulose, Sephadex G75 chromatography and a terminal isoelectric focusing step. An inhibitory protein was obtained and was identified by its physicochemical and inhibitory properties as the .epsilon. subunit of E. coli ATPase. The other inhibitory fraction observed in the purification procedure consisted of aggregated .epsilon. subunits.