Expression and purification of recombinant NA in mammalian cells.

Human TB-NA (Hokkaido) fused to the Tetrabrachion stalk (Fig. 1B) was cloned into the pApex-3 vector and expressed in HEK293T cells. Media, flow-through, and purified NA were loaded onto SDS-PAGE and detected by anti-FLAG WB (left panel) or stained by Coomassie (right panel). Secreted FLAG-reactive NA was detected by anti-FLAG WB. Based on the anti-FLAG WB the column flow-through did not contain any residual FLAG reactive NA.