Terpendole E and its Derivative Inhibit STLC‐ and GSK‐1‐Resistant Eg5

Terpendole E is first natural product found to inhibit mitotic kinesin Eg5, but its inhibitory mechanism remains to be revealed. Here, we report the effects of terpendole E and 11ketopaspaline (a new natural terpendole E analogue) on the Eg5-microtubule interaction and in several Eg5 mutants. 11-Ketopaspaline is a shunt product from terpendole E, and it shows potent inhibitory activity against the microtubule-stimulated ATPase activity of Eg5. Unlike other Eg5 inhibitors, such as S-trityl-L-cysteine (STLC) and GSK-1, both terpendole E and 11-ketopaspaline only partially inhibited Eg5-microtubule interaction. Furthermore, terpendole E and 11-ketopaspaline inhibited several Eg5 mutants that are resistant to STLC (Eg5(D130A), Eg5(L214A)) or GSK-1 (Eg5(I299F), Eg5(A356T)), but with the same extent of inhibition against wild-type Eg5. Because Eg5(D130A) and Eg5(L214A) show cross-resistance to most known Eg5 inhibitors, which bind the L5 loop, these results suggest that terpendole E and its analogues have a different binding site and/or inhibitory mechanism to those for L5 loop-binding type Eg5 inhibitors.