SDS gel showing trypsin digestion of the C-terminal region (a.a. 191–430) of P22 CP. Lane 1 is the undigested C-terminal region, 2 is molecular weight markers, and 3 and 4 are of samples taken after 30 or 60 minutes of digestion at 20 °C, respectively. The black arrow points to the band corresponding to residues 223–349 (telokin domain). The white arrow points to a band with faster electrophoretic mobility that, when sequenced by MS/MS MALDI-TOF-TOF mass spectrometry, revealed multiple fragments with sequences all falling within in the 223–349 range.