Activation of the Exocyst Tethering Complex for SNARE Complex Regulation and Membrane Fusion

A major challenge for a molecular understanding of membrane trafficking has been the elucidation high resolution structures large, multisubunit tethering complexes (MTCs) that spatially and temporally control intracellular fusion. Exocyst is hetero-octameric protein complex, proposed to tether secretory vesicles at plasma membrane, provide quality SNARE-mediated Breakthroughs in methodologies, including sample preparation, biochemical characterization, fluorescence single-particle cryo-EM, are providing critical insights into structure function exocyst. We investigating how yeast exocyst interacts with SNARE proteins complex formation Intriguingly, fully assembled weakly individual SNAREs, complexes, regulator Sec1, despite previously observed robust binding recombinant proteins. Using an auxin-inducible degradation system mutant strains, we purified subcomplexes showed several have increased affinities different SNAREs. Negative stain EM was used visualize subcomplex, as well 3D activated complex. Comparison negative images cryo-EM revealed subunits become more dynamic accessible interactions. propose needs undergo one or conformational changes, order efficiently interact regulate