Extracted protein was recognized by anti-CFA/I mouse antiserum (Figure 1). Matrix assisted laser desorption ionization-time of flight (MALDI-TOF) showed a predominant peak at a mass of 15,525 daltons for the tag-less CFA/I/II/IV protein (Figure 1), and 17,307 daltons for the 6xHis-tagged MEFA protein, the expected molecular mass for both proteins.