Definition of surface-exposed epitopes on the (Ca(2+)-Mg2+)-ATPase of sarcoplasmic reticulum.

Epitopes for monoclonal antibodies binding to the native (Ca(2+)-Mg2+)-ATPase have been defined by studying binding to sets of hexameric peptides synthesized on plastic pegs. Epitopes have been confirmed by demonstrating the binding of anti-peptide antibodies to the ATPase. A method is presented for definition of surface-exposed epitopes using polyclonal antibodies. Three surface-exposed epitopes have been defined in the nucleotide-binding domain of the ATPase, suggesting considerable surface exposure of this region. Other surface-exposed epitopes have been located in the region of the fourth stalk domain.