Western blot analysis of V5 tag was performed by loading 20 µg whole cell extracts of untransfected HEK-293 and HEK-293 transiently overexpressing V5-His-LacZ using Novex® NuPAGE® 4-12% Bis-Tris gel (Product # NP0321BOX), XCell SureLock Electrophoresis System (Product # EI0002), and Novex® Sharp Pre-Stained Protein Standard (LC5800). Proteins were transferred to a PVDF membrane and blocked with 5% skim milk for 1 hour at room temperature. V5-His-LacZ was detected at ~117 kDa using V5-HRP Mouse Monoclonal Antibody (Product # R961-25)