In vitro binding of NS1 proteins with p85β. (A) Expression and purification of GST and GST-p85β protein in E.coli BL21. Purified GST and GST-p85β proteins were resolved in SDS-PAGE and examined by direct staining with Coomassie Blue; M: molecular weight standard. (B) In vitro translation of different NS1 proteins using NS1-expressing plasmids and TNT T7 Quick Coupled Transcription/Translation Systems. The in-vitro translated proteins were identified by Western blot using Streptavidin-HRP as the detecting agent. (C) GST pull-down assay. GST- or GST-p85β-binding magnetic beads were incubated with NS1 proteins translated in vitro. The bound proteins were subjected to Western blotting with anti-NS1 antibody.