IDENTIFICATION OF SUBUNITS REQUIRED FOR THE CATALYTIC ACTIVITY OF THE F1-ATPASE

F1(alphabeta) complexes containing equimolar ratios of the alpha and beta subunits have been shown to function as active ATPases, whereas individually isolated alpha and beta subunits show no real ATPase activity. These results indicate that the single-copy subunits are not required for F1-ATPase activity. The minimal F1(alphabeta)-core complexes exhibit, however, lower rates and some different properties from those of their parent whole F1 or alpha3beta3gamma complexes. It is therefore concluded that for obtaining a full spectrum of the characteristic functional properties of an F1-ATPase the presence of the F1-gamma subunit is also required. The implications of these findings on the subunit location of both catalytic and noncatalytic nucleotide binding sites is discussed.