Use of monoclonal antibodies in immuno-electron microscopy for the determination of subunit stoichiometry in oligomeric enzymes. There are three alpha-subunits in the F1-ATPase of Escherichia coli.

The subunit stoichiometry of oligomeric enzymes can be determined by immuno-electron microscopy using monoclonal antibodies against the individual subunits. Monoclonal antibodies against native F1-ATPase of Escherichia coli were prepared that were specific for the alpha-subunit. The immune complexes of F1 and monoclonal antibodies were isolated. Electron microscopy revealed the presence of three immunoglobulins per molecule of F1-ATPase. This unequivocally demonstrates an alpha 3 stoichiometry for the F1-ATPase of E. coli.