FIG. 2.

Mass spectrometry of proteolytic fragments of NSP4. Purified C90 (50 μg) was digested with trypsin (0.5 μg) for 2 h at 0°C or V8 protease (0.5 μg) for 60 min at 32°C. The reactions were terminated by the addition of protease inhibitors (0.5 mM Pefabloc for trypsin and 5 μM dichloroisocumarin for V8 protease). Mass spectra for digested and undigested samples were obtained by MALDITOF mass spectrometry. Shown are undigested C90 (A), trypsin-digested C90 (B), and V8 protease-digested C90 (C).