The anti-tumor antibiotic PD 113,271 binds to microtubule-associated protein 1B (MAP1B)

PD 113,271 and fostriecin are structurally related phosphate monoesters with potent cytotoxicity against several tumor cell lines. Although there have been several biological studies on fostriecin such as that on protein phosphatase (PP) 2A inhibition and its mode of action, little is known about PD 113,271. In the present study, we identified microtubule-associated protein (MAP) 1B as a binding protein of PD 113,271 using phage display biopanning. Phages that expressed the highly basic region of MAP1B bound to the immobilized PD 113,271. In addition, PD 113,271 bound to MAP1B in the lysate of human liver cells. Moreover, we identified that PD 113,271 directly interfered with MAP1B binding to microtubules and induced a morphological abnormality in the distribution of MAP1B in cells. These results showed that PD 113,271 binds to the tubulin binding domain of MAP1B and may be useful for studying MAP1B function.