The Bacterial Effector VopL Organizes Actin into Filament-like Structures.
Zahm JA, Padrick SB, Chen Z, Pak CW, Yunus AA, Henry L, Tomchick DR, Chen Z, Rosen MK.Cell. 2013 Oct 10;155(2):423-34.
Representative example of 2Fo-Fc electron density contoured at 1σ and the refined model, in the region inside the box drawn in panel A. In this region, the VCD chain A β1−β2 hairpin interacts with actins 1 and 2, forming side contacts with the former, and tip contacts with the latter. The colors of carbon atoms of VCD chain A, chain B, actin 1, and actin 2 correspond to the colors of the corresponding representations depicted in panel A. Nitrogen and oxygen atoms are colored red and blue, respectively. VopL secondary structure elements and residues are labeled.
VopL is an effector protein from Vibrio parahaemolyticus that nucleates actin filaments. VopL consists of a VopL C-terminal domain (VCD) and an array of three WASP homology 2 (WH2) motifs. Here, we report the crystal structure of the VCD dimer bound to actin. The VCD organizes three actin monomers in a spatial arrangement close to that found in the canonical actin filament. In this arrangement, WH2 motifs can be modeled into the binding site of each actin without steric clashes. The data suggest a mechanism of nucleation wherein VopL creates filament-like structures, organized by the VCD with monomers delivered by the WH2 array, that can template addition of new subunits. Similarities with Arp2/3 complex and formin proteins suggest that organization of monomers into filament-like structures is a general and central feature of actin nucleation.
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