Abstract
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.
Highlights
Polarized growth is crucial for various biological processes across yeast and filamentous fungi, which is achieved through the cytoskeleton-based directional transport of cargo to polarized domains [1]
Rho GTPase Cdc42 is essential for the control of polarized growth during bud emergence, by recruitment of a yeast-specific complex called the polarisome, which is comprised of formin Bni1, nucleation-promoting factor (NPF) Bud6, Pea2, scaffolding protein Spa2 and receptor protein Epo1 [2,3,4]
To determine the accurate mass of the Bem3CC1 and Epo1CC2-CC4 complex, we performed analytical gel filtration combined with multiangle lighting scattering (MALS)
Summary
Polarized growth is crucial for various biological processes across yeast and filamentous fungi, which is achieved through the cytoskeleton-based directional transport of cargo to polarized domains [1]. Rho GTPase Cdc is essential for the control of polarized growth during bud emergence, by recruitment of a yeast-specific complex called the polarisome, which is comprised of formin Bni, nucleation-promoting factor (NPF) Bud, Pea, scaffolding protein Spa and receptor protein Epo1 [2,3,4]. Distinct and not fully characterized protein complexes organize the contact sites between the PM and the endoplasmic reticulum. Bem localizes to the sites of polarisome growth through its C-terminal Rho GTPaseactivating protein domain, which negatively regulates a Rho-type GTPase Cdc42 [7,8,9]
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