High pressure promotes binding of the allosteric inhibitor Zn2+‐cyclen in crystals of activated H‐Ras
Abstract
In this work, we experimentally investigate the potency of high pressure to drive a protein toward an excited state where an inhibitor targeted for this state can bind. Ras proteins are small
GTPases cycling between active GTP-bound and inactive GDPbound states. Various states of GTP-bound Ras in active conformation coexist in solution, amongst them, state 2 which binds
to effectors, and state 1, weakly populated at ambient conditions, which has a low affinity for effectors. Zn2+-cyclen is an allosteric inhibitor of Ras protein, designed to bind specifically to the state 1. In
H-Ras(wt).Mg2+.GppNHp crystals soaked with Zn2+-cyclen, no binding could be observed, as expected in the state 2 conformation which is the dominant state at ambient pressure. Interestingly, Zn2+-cyclen
binding is observed at 500 MPa pressure, close to the nucleotide, in Ras protein that is driven by pressure to a state 1 conformer. The unknown binding mode of Zn2+-cyclen to H-Ras can thus be fully
characterized in atomic details. As a more general conjunction from our study, high pressure x-ray crystallography turns out to be a powerful method to induce transitions allowing drug binding in
proteins that are in low-populated conformations at ambient conditions, enabling the design of specific inhibitors.