Figure 1. Expression of Hemagglutinin protein in plants and purification. (A) A schematic of the HA0 protein structure with described domains. (B) Schematic of HA0 protein expressed in planta lacking transmembrane and cytoplasmic domains and containing poly-His tag and HDEL retention sequence. (C) Three representative lots of HA protein analyzed by SDS-PAGE (left panel; lanes 3–5; 0.5 µg/lane). Recombinant HA protein from Sino Biological Inc. was used as a positive control (lane 2; 0.38 µg/lane). Precision plus protein molecular weight standards were used as size markers (lane 1). The same proteins were loaded at 7ng/lane and visualized by anti-HA Western, using an HA-specific monoclonal antibody (Sino Biological Inc.).