Cryo-EM Structure of the Exocyst Complex

The exocyst is an evolutionarily conserved octameric protein complex that mediates the tethering of post-Golgi secretory vesicles to the plasma membrane during exocytosis, and is implicated in many cellular processes such as cell polarization, cytokinesis, ciliogenesis and tumor invasion. Using cryo-electron microscopy (cryo-EM) and chemical cross-linking mass spectrometry (CXMS), we solved the structure of the Saccharomyces cerevisiae exocyst complex at an average resolution of 4.4 Å. Our model revealed the architecture of the exocyst, and led to the identification of the helical bundles that mediate the assembly of the complex at its core. Sequence analysis suggests that these regions are evolutionarily conserved across eukaryotic systems. Further cell biological studies suggest a mechanism for exocyst assembly that leads to vesicle tethering at the plasma membrane.