Cys mutants in functional regions of Sticholysin I clarify the participation of these residues in pore formation

► Replacement of Glu2, Phe15 and Arg52 by Cys in rStI did not change its conformation. ► Substitution of Arg52 by Cys provoked changes in rStI's permeabilizing activity. ► Replacement of Glu2 and Phe15 by Cys did not elicit any observable effect. ► StI E2C's dimmers stabilized by a disulfide bond enhanced rStI's pore forming ability. ► These oligomers linked through their amino termini could facilitate pore formation.