2 research outputs found
Evidence for an Induced-Fit Process Underlying the Activation of Apoptotic BAX by an Intrinsically Disordered BimBH3 Peptide
Apoptotic
BAX protein functions as a critical gateway to mitochondria-mediated
apoptosis. A diversity of stimuli has been implicated in initiating
BAX activation, but the triggering mechanism remains elusive. Here
we study the interaction of BAX with an intrinsically disordered BH3
motif of Bim protein (BimBH3) using ESR techniques. Upon incubation
with BAX, BimBH3 binds to BAX at helices 1/6 trigger site to initiate
conformational changes of BAX, which in turn promotes the formation
of BAX oligomers. The study strategy is twofold: while BAX oligomerization
was monitored through spectral changes of spin-labeled BAX, the binding
kinetics was studied by observing time-dependent changes of spin-labeled
BimBH3. Meanwhile, conformational transition between the unstructured
and structured BimBH3 was measured. We show that helical propensity
of the BimBH3 is increased upon binding to BAX but is then reduced
after being released from the activated BAX; the release is due to
the BimBH3-induced conformational change of BAX that is a prerequisite
for the oligomer assembling. Intermediate states are identified, offering
a key snapshot of the coupled folding and binding process. Our results
provide a quantitative mechanistic description of the BAX activation
and reveal new insights into the mechanism underlying the interactions
between BAX and BH3-mimetic peptide