Positive Selection of Specific Antibodies Produced against Fusion Proteins

A method for the positive selection of specific antibodies for target proteins expressed as fusion proteins for the production of antiserum is presented. As proof of concept, the fusion protein FLAG::His::GFP::His::FLAG was expressed in Escherichia coli, purified, and used for the immunization of rabbits. The obtained serum was precleared via protein A affinity. A CusF::FLAG fusion protein was expressed in the periplasm of E. coli and purified. GFP without tags was also expressed in E. coli and purified via organic extraction. These proteins were then coupled to NHS-activated sepharose and used for the positive selection of Anti-GFP and Anti-FLAG antibodies. The obtained sera were tested for their specificity against different protein samples and fusion proteins in Western blots. A high specificity of the antibodies could be achieved by a single affinity chromatography step. In general, we advise to express the target protein with different tags and in different E. coli compartments for antibody production and affinity chromatography.