FIG. 4.

Cell localization of neuraminidase activity. A total of 4 × 10⁷ whole cells (WC), 4 × 10⁷ lysed protoplasts (P), 20 μl of culture supernatant (S), and 200 μg of purified CWE from wild-type BBR1 (open bars), the NANP-1 mutant (gray bars), and the NANHP-1 mutant (cross-hatched bars) were assayed for neuraminidase activity by using the fluorometric assay with MUAN as a substrate. The error bars indicate 1 standard deviation of the mean calculated by using the averages from at least three independent experiments.