Stoichiometry of actin and phalloidin binding: one molecule of the toxin dominates two actin subunits.
Sonication of F-actin in the absence of added ATP in the solvent induces denaturation of the actin. When phalloidin is added to actin at the molar ratio of 1:2, the denaturation is completely inhibited. More directly, pelleting experiments have indicated that the binding of phalloidin to actin subunits is saturated at the same molar ratio. The protection of F-actin from heat denaturation or depolymerization with 0.6 M KI is also complete with one molecule of the toxin over two actin subunits. Therefore, it is concluded that the binding ratio of phalloidin and the actin subunit is not 1:1 but 1:2.
D000199:Actins / Q000378:metabolism*; D000255:Adenosine Triphosphate; D001665:Binding Sites; D009842:Oligopeptides / Q000378:metabolism*; D010590:Phalloidine / Q000378:metabolism*; D011485:Protein Binding; D011489:Protein Denaturation; D012997:Solvents; D013010:Sonication
D000199:Actins; D009842:Oligopeptides; D012997:Solvents; D010590:Phalloidine; D000255:Adenosine Triphosphate