Purified recombinant sweet potato MT-I and MT-II proteins. A. MT-I proteins and B. MT-II proteins 15% SDS-PAGE analysis. Crude extracts (5 μg protein) from E. coli (M15) transformed with pQE30 (lane 1) or with pQE31- MT-I (lane 2) or pQE31- MT-II were analyzed by 15% (w/v) SDS-PAGE, and then the gels were stained with Coomassie brilliant blue G-250. Molecular masses of standard proteins were indicated at the left of the figure. His-tagged MT-I protein or MT-II was purified by Ni2+-chelated affinity chromatography (lane 3). C. MT-I proteins and D. MT-II proteins analyzed by Western blot. The gels were transferred onto PVDF membranes that were probed with a 1:1000 (v/v) dilution of mouse antibodies raised against MT using goat-anti-mouse alkaline phosphatase as the secondary antibody. The experiments were done twice and a representative one is shown. “M” indicated the see Blue™ pre-stained markers for SDS-PAGE. Each data show the mean ± SD of one experiment performed in triplicate.