FIG. 2.

Purification of the fructokinase Frk. Samples (1 μg of protein) were separated in a sodium dodecyl sulfate-10% polyacrylamide gel and stained with Coomassie brilliant blue R-250. Lane 1, molecular mass standard; lane 2, negative control [a crude extract of E. coli BL21 (DE3) containing pET28a(+)]; lane 3, crude extract of IPTG-induced cells of E. coli BL21 (DE3) containing pFrk; lane 4, eluate with sonication buffer containing 150 mM imidazole from cobalt-based affinity column; lane 5, purified Frk after elimination of the six-His tag by thrombin cleavage.