Figure 2.

Specific interactions between elicitins and high-affinity sites located on tobacco plasma membranes: ligand replacement kinetics. (A) Kinetics of specific displacement of ¹²⁵I-cryptogein bound to plasma membrane by unlabeled elicitins. Plasma membrane (50 μg of protein) was incubated with 2 nM ¹²⁵I-cryptogein during 120 min. Then, replacement was initiated by the addition of 10 μM unlabeled elicitins (zero time). Data are expressed as the percentages of the initial amount of ¹²⁵I-cryptogein specifically bound (∼250 fmol/mg plasmalemma protein) before addition of unlabeled elicitins. This experiment was repeated three times, and the data presented correspond to a representative experiment. (B) Relationship between the initial rate of replacement and the affinity of elicitins for sterols (three measurements of three independent replicates). ⋄, control, without unlabeled elicitin addition; ▴, cryptogein; ▵, X24; ▪, Y47F; □, Y47G; ○, Y87F.