C395S bomapin mutant, representing reduced form of bomapin, does not enhance proliferation of K562 cells. (A) SDS-PAGE analysis (followed by Coomassie blue staining) of the E. coli expressed and purified recombinant C395S bomapin mutant (lane 1) and the mutant protein incubated with a 4-fold molar excess of trypsin (lane 2). (B) Cellular localization of C395S-bomapin-EGFP in stably transfected K562 cells. (C) Proliferation of the stably transfected multiclonal K562 cells expressing bomapin-EGFP, C395S-bomapin-EGFP, and EGFP alone, as measured by manual cell counting. Higher proliferation of K562 cells expressing wt bomapin, compared to Fig. 2B, is due to higher generation number of the cells that were used in this experiment.