TETRAHEDRON LETTERS Tetr~edronLet~rs40(1999) 887-890 Pergamon Direct Observation of Binding between Biotinylated Okadaic Acids and Protein Phosphatase 2A Monitored by Surface Plasmon Resonance Keiichi Konoki, Naoyuki Sugiyama, Michio Murata, and Kazuo Tachibana* Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan Received 18 September 1998; revised 12 November 1998; accepted 17 November 1998 Abstract : Two biotin conjugates ofokadaic acid were synthesized for evaluating their interactions with protein phosphatase 2A by surface plasmon resonance (SPR). C7-biotinylated okadaic acid revealed strong binding affinity to the enzyme, while Cl-biotinylated derivative being devoid of affinity, implying that the C7-biotin conjugate is a useful tool for biochemical studies of protein phosphatase 2A. © 1999 Elsevier Science Ltd. All rights reserved. Keywords: Okadaicacid; Surfaceplasmon resonance; Protein phosphatases Reversible phosphorylation of proteins is catalyzed by both protein kinase and protein phosphatase, through which eukaryotic cells translate extracellular signals to intracellular events. Several natural products such as okadaic acid (1), ~ microcystin, tautomycin and calyculin A are known to bind and inhibit protein phosphatases 1 and 2A (PP2A), resulting in accumulation of phosphorylated proteins in cells of various organs.2) The binding of these inhibitors to protein phosphatases has been mainly investigated by replacement experiments using a radioligand such as [27-3H]okadaic acid 3) or by monitoring the enzymatic activity. 4) Among them, okadaic acid (1) is the most potent PP2A inhibitor, and now regarded as a standard reagent for biological studies of protein phosphatases. 2) 43 O ~ OH .Ac- o47 . ° - " oH I 40 Okadaic acid (1) Recent progress in optical-biosensing technologies has made it possible to investigate the kinetics of diverse interactions between biomolecules such as protein-protein, protein-peptide, and DNA-protein. Surface plasmon resonance (SPR) is one of these apparatus, by which receptor-ligand interactions are observed in real time as changes of local refractive index. 5) Once a ligand is biotinylated without loss of its binding affinity, the interaction with its receptor can be monitored using the immobilized ligand on a sensor chip via avidin-biotin binding. 6) Besides this, the biotinylation of a ligand enables us to adopt methodologies widely used in 0040-4039/99/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved. PlI: S0040-4039(98)02474-5