pJoseph2: a family of plasmids as positive controls for bacterial protein expression, transfections, and western blots.

Epitope tagging represents a powerful strategy for expedited identification, isolation, and characterization of proteins in molecular biological studies, including protein-protein interactions. We aimed to improve the reproducibility of epitope-tagged protein expression and detection by developing a range of plasmids as positive controls. The pJoseph2 family of expression plasmids functions in diverse cellular environments and cell types to enable the evaluation of transfection efficiency and antibody staining for epitope detection. The expressed green fluorescent proteins harbor five unique epitope tags, and their efficient expression in Escherichia coli, Drosophila Schneider's line 2 cells, and human SKOV3 and HEK293T cells was demonstrated by fluorescence microscopy and western blotting. The pJoseph2 plasmids provide versatile and valuable positive controls for numerous experimental applications.