Crystal Structure of the Epo1-Bem3 Complex for Bud Growth

Tubules of the endoplasmic reticulum (ER) spread into the buds of yeast by an actin-based mechanism and, upon entry, become attached to the polarisome, a proteinaceous micro-compartment below the tip of the bud. The minimal tether between polarisome and cortical ER is formed by a protein complex consisting of Epo1, a member of the polarisome, Scs2, a membrane protein of the ER and Cdc42 guanosine triphosphatase-activating protein Bem3. Here, we report the crystal structure of a complex between Epo1 and Bem3. In addition, we characterize through the hydrogen/deuterium (H/D) exchange assay the interface between Scs2 and Epo1. Our findings provide a first structural insight into the molecular architecture of the link between cortical ER and the polarisome.

Automated summary

The tubules of endoplasmic reticulum (ER) spread into yeast buds through an actin-based mechanism and become attached to the proteinaceous micro-compartment called polarisome. The minimal tether between polarisome and cortical ER is formed by a protein complex consisting of Epo1, Scs2, and Cdc42 guanosine triphosphatase-activating protein Bem3. This study presents the crystal structure of the complex between Epo1 and Bem3, providing a structural insight into the link between cortical ER and polarisome.