FIG. 3.

Semiquantitative analysis of streptokinase production. By casein agar plate analysis (11), streptokinase production was assayed in culture supernatants of strains NZ131 (row A), NZ131 Δska::Em^r (row B), and NZAN5 (row C), which corresponds to NZ131 Δska::Em^r containing the skc5 gene from S. equisimilis H46A. Wells 1 contain undiluted supernatants, and the following wells contain three 10-fold supernatant dilutions. Row D shows three wells with streptokinase at 1, 0.5, and 0.1 U (in numerical order of the wells). The clearance in B1, of NZ131 Δska::Em^r, is due to background protease activity. Streptokinase is produced in equal amounts by NZ131 and NZAN5 (A3 and C3) but is not produced by NZ131 Δska::Em^r (B3).