N-WASP is competent for downstream signaling before full release from autoinhibition

Abstract

Allosteric regulation of intrinsically disordered proteins (IDPs) is still vastly understudied compared to the counterpart of structured proteins. Here we used molecular dynamics simulations to characterize the regulation of the IDP N-WASP by the binding of its basic region with intermolecular and intramolecular ligands (PIP2 and an acidic motif, respectively). The intramolecular interactions keep N-WASP in an autoinhibited state; PIP2 binding frees the acidic motif for interacting with Arp2/3 and thereby initiating actin polymerization. We show that PIP2 and the acidic motif compete in binding with the basic region. However, even when PIP2 is present at 30% in the membrane, the acidic motif is free of contacts with the basic region ("open" state) in only 8.5% of the population. The very C-terminal three residues of the A motif are crucial for Arp2/3 binding; conformations where only the A tail is free are present at a much higher population than the open state (40- to 5-fold, depending on the PIP2 level). N-WASP is thus competent for Arp2/3 binding before it is fully freed from autoinhibition.

Protein conformational ensembles in function: roles and mechanisms

“…[65][66][67][68][69] The ensembles are also impacted by the inherent liquefied droplets in the dynamic spatial structure of the cell, which extends from small complexes and assemblies to micrometer scales and coordinates cellular behavior. [70][71][72][73][74] Below, we first discuss allostery, 40,[75][76][77][78][79][80][81][82][83] a hallmark of the functional role of conformational ensembles, followed by examples drawn from kinases and small GTPases. The references above provide more.…”

“…Below, we first discuss allostery, 40,75–83 a hallmark of the functional role of conformational ensembles, followed by examples drawn from kinases and small GTPases. The references above provide more.…”