Construction of pET21a-E2 recombinant vector. (a) Lane 1, Isolated pET21a-E2 gene. (b) Lane 1, Single restriction of pET21a-E2 with NdeI. (c) Lane 1, Double restriction of pET21a-E2 with NdeI and HindIII restriction enzymes; Lane M, GeneRulerTMDNA ladder mix (Fermentas Cat # SM0331).