Fig. 5: An allosteric competition model explains WRC activation by Rac1 binding to the A site.
From: Structures reveal a key mechanism of WAVE regulatory complex activation by Rac1 GTPase
a, b Coomassie blue-stained SDS-PAGE gels showing GST-Rac1P29S (loaded with GDP or GMPPNP) pull-down of WRCD-Rac1 bearing the indicated mutations: WAVE1∆PPP in (A) (replacing 131PPPLNI136 with a GSGSGS linker) and WAVE1Y151E or Sra1R87C in (B). c Pyrene-actin polymerization assays measuring the activities of WRCD-Rac1 used in (A-B). Reactions use the NMEH20GD buffer and contain 3.5 µM actin (5% pyrene-labeled), 10 nM Arp2/3 complex, and 100 nM WRCD-Rac1 carrying indicated mutations. d A “door wedge” model describing the allosteric competition mechanism underlying WRC activation by Rac1 binding to the A site. WRC activation requires Rac1 binding to the A site to swing the door (A site in Sra1 and α4-loop-α5 in WAVE1) against the wedge (Y151 and the “stem” sequence) inserted into the door hinge. The “tug-of-war” between Rac1 binding and the tyrosine lock determines the activity level of the WRC. Phosphorylation (blue dot) of the released Y151 further shifts the equilibrium to provide an additional control of the strength and duration of WRC activation. Note that for clarity, majority of Sra1 and other WRC components not directly involved in activation are not shown in the cartoon. Source data for a–c are provided as a Source Data file.
