Purified mouse monoclonal IgG antibody against the C-terminal AviTag™ peptide sequence (AbC) has been conjugated to Sepharose resin to create an affinity purification method for C-terminal AviTag™ fusion proteins. Cell extracts generated by common lysis methods can be used as long as reducing agents were NOT used in their preparation. High salt concentrations and most ionic detergents do not inhibit the binding capacity of the resin.