Purification of DCG-04. A silver stained SDS-gel of different purification steps by DCG-04. Lane 1 shows the crude T. thermophila supernatant, lane 2 the supernatant after the addition of DCG-04 and subsequent extraction by means of streptavidin beads. In lane 3 the supernatant of beads that have been washed and boiled in SDS buffer is shown. The enriched protease fraction mainly consists of bands of approximately 22-28 kD.