Lane M, molecular-mass markers (in kDa); lane 1, total lysate of E. coli BL21(DE3)pLysS pET23b-FRU cells; lane 2, total lysate of control E. coli BL21(DE3)pLysS pET23b cells; lanes 3 and 4, wash fractions with buffer W; and, lane 5, fraction eluted by 0.5 M imidazole.