Development of Biotin–Avidin Technology to Investigate Okadaic Acid-Promoted Cell Signaling Pathway

Four biotin conjugates of okadaic acid were synthesized for evaluating their interactions with protein phosphatase 2A (PP2A) by surface plasmon resonance (SPR). C7-biotinylated okadaic acid exhibited the strongest binding affinity to the enzyme, while C1-biotinylated derivative was devoid of affinity. C24- or C27-biotinylated okadaic acid showed moderate affinity to the enzyme. In the wake of this finding, a biotinyl photoaffinity probe was introduced into 7-OH of okadaic acid. Photoaffinity labeling followed by SDS-PAGE analysis indicated that the okadaic acid derivative clearly labeled PP2A. Furthermore, three proteins were also labeled in crude extracts of a marine sponge Halichondria okadai. All these results imply that the C7-biotin conjugate is a versatile reagent for biochemical studies of okadaic acid-binding proteins including PP2A.