The
binding site of the macrolides laulimalide and peloruside A,
which is different from that of the clinically useful drugs paclitaxel/taxol
and ixabepilone (
tax site
), is known to be between two
adjacent β-tubulin units (
ext site
). Here, we report
our study of the binding of these molecules to an α1β1/α2β2-tubulin
“tetramer” model. AutoDock 4.2.6//AutoDock Vina dockings
predicted that the affinities of laulimalide and peloruside A for
the
tax site
are quite similar to those for the
ext site
. However, molecular dynamics (MD) simulations indicated
that only when these two ligands are located at the
ext site
, there are contacts that help stabilize the system, favoring the
β1/β2 interactions. The binding affinity of laulimalide
for this site is stronger than that of peloruside A, but this is compensated
for by additional β1/β2 contacts that are induced by peloruside
A. MD studies also suggested that epothilones at the
tax site
and either laulimalide or peloruside A at the
ext site
cause similar stabilizing effects (mainly linking the M-loop of
β1 and loop H1–B2 of β2). In a “hexamer”
model (3 units of αβ-tubulin), the effects are confirmed.
Metadynamics simulations of laulimalide and peloruside A, which are
reported for the first time, suggest that peloruside A produces a
stronger change in the M-loop, which explains the stabilization of
the β1/β2 interaction.