Influence of the α-, β- and γ-subunits of the energy-transducing adenosine triphosphates from Micrococcus lysodeikticus in the immunochemical properties of the protein and in their reconstitution studied by a radioimmunoassay method

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Abstract
A sensitive and specific radioimmunoassay of the energy-transducing F1-ATPase (EC 3.6.1.3) of M. lysodeikticus (M. luteus) was developed. The assay was extended to the .alpha.-, .beta.- and .gamma.-subunits of the enzyme. These subunits were isolated and cross-reactions were studied. The immunochemical properties of the .alpha.- and .beta.-subunits differed and the .gamma.-subunit showed an intermediate behavior between that of the .alpha.- and .beta.-subunits. Each subunit of M. luteus F1-ATPase has its own identity; conformational antigenic determinants and/or cooperative antigenic sites arise from subunit assembly. Equimolecular amounts of .alpha.- and .beta.-subunits (up to 3 copies of each) partially reconstituted the immunochemical properties of the ATPase molecule, and addition of 2 mol of .gamma.-subunit per mol of .alpha.3.beta.3 complex improved reconstitution. The 1st reconstitution of biological activity of this ATPase by assembly of the isolated subunits is described, and earlier proposals on the stoichiometry of the .alpha.3.beta.3.gamma.2 type for M. luteus F1-ATPase are supported. The radioimmunoassay method enables study of the homologies between different energy-transducing ATPases and their constituent polypeptides even though the primary structure of these complex proteins has not yet been determined.

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