C. jejuni GGT purification. (A) Analysis of the purification of C. jejuni GGT by migration on SDS-PAGE gel and Coomassie blue staining. M: size marker. (1) Supernatant after precipitation and dialysis, (2) After the first ion exchange chromatography, (3) Final elution. The black arrows indicate the 40 and 20 kDa bands which correspond to the expected molecular weights of the large and small subunits of C. jejuni GGT, respectively. The black dotted boxes represent the gel bands which were cut and analyzed by mass spectrometry. (B) Mass spectrometry results. After extraction and protein digestion, (1) amino-acids found in the 40 kDa band (in grey) cover 73.6% of the protein sequence of the large subunit of C. jejuni GGT; (2) amino-acids found in the 20 kDa band cover 68.8% of the protein sequence of the small subunit.