Analysis of the aplyronine A-induced protein-protein interaction between actin and tubulin by surface plasmon resonance.

The antitumor macrolide aplyronine A induces protein-protein interaction (PPI) between actin and tubulin to exert highly potent biological activities. The interactions and binding kinetics of these molecules were analyzed by the surface plasmon resonance with biotinylated aplyronines or tubulin as ligands. Strong binding was observed for tubulin and actin with immobilized aplyronine A. These PPIs were almost completely inhibited by one equivalent of either aplyronine A or C, or mycalolide B. In contrast, a non-competitive actin-depolymerizing agent, latrunculin A, highly accelerated their association. Significant binding was also observed for immobilized tubulin with an actin-aplyronine A complex, and the dissociation constant KD was 1.84μM. Our method could be used for the quantitative analysis of the PPIs between two polymerizing proteins stabilized with small agents.