Sec3 (also known as ExoC1) is a component of the exocyst complex, which mediates the tethering of post-Golgi secretory vesicles to the plasma membrane and promotes the assembly of the SNARE complex for membrane fusion. The exocyst is also involved in other cell processes such as cell polarisation, primary ciliogenesis, cytokinesis, and tumourigenesis and metastasis [1]. This complex has an elongated shape consisting of packed long rods, a structure that is shared among the Complex Associated with Tethering Containing Helical Rods (CATCHRs) proteins from related complexes such as Conserved Oligomeric Golgi complex (COG) and Golgi-Associated Retrograde Protein complex (GARP) [2,3,4]. Subunits of these complexes, apart of helical bundles, they usually have a coiled-coil (CC) region at the N-terminal. Sec3 is described as a membrane-anchoring component which serves as a spatial landmark in the plasma membrane for incoming secretory vesicles. This entry represents the middle coiled-coil region (known as the 'CorEx motif') of Sec3 which forms an antiparallel 'zipper' with Sec5 subunit to assemble with Sec6-Sec8 zipper and form a four-helical bundle [3].

1: The glycine transporter GLYT1 interacts with Sec3, a component of the exocyst complex. Cubelos B, Gimenez C, Zafra F; Neuropharmacology. 2005;49:935-944. PMID:16181645

2: Crystal structure of Sec10, a subunit of the exocyst complex. Chen J, Yamagata A, Kubota K, Sato Y, Goto-Ito S, Fukai S; Sci Rep. 2017;7:40909. PMID:28098232

3: Cryo-EM structure of the exocyst complex. Mei K, Li Y, Wang S, Shao G, Wang J, Ding Y, Luo G, Yue P, Liu JJ, Wang X, Dong MQ, Wang HW, Guo W; Nat Struct Mol Biol. 2018;25:139-146. PMID:29335562

4: Homology and Modular Evolution of CATCHR at the Origin of the Eukaryotic Endomembrane System. Santana-Molina C, Gutierrez F, Devos DP; Genome Biol Evol. 2021; [Epub ahead of print] PMID:34061181