SDS-PAGE and Western blot patterns of recombinant M2 protein. Lane M: protein molecular weight marker; lanes 1 and 2: SDS-PAGE patterns of the soluble rM2 and refolded rM2 from E. coli inclusion, respectively. Soluble rM2 appears as a band of 17 kDa while M2 prepared from the E. coli inclusion appears as a protein doublet which the lower band is mature rM2 and the upper band is rM2 linked with pelB1 leader peptide of pET20b(+) (21 kDa). Lanes 3 and 4: Western blot patterns of the soluble rM2 and pelB1-linked M2, respectively. For the Western blotting, strips of nitrocellulose membrane (NC) blotted with SDS-PAGE separated-rM2 were incubated with mouse anti-6x-histidine antibody, goat anti-mouse immunoglobulin-alkaline phosphatase conjugate and BCIP/NBT substrate, respective. Uppermost band in lane 4 (arrow) is rM2 dimer. Numbers at the left are relative molecular masses (Mr) of proteins.