Functions as a component of the nuclear pore complex (NPC) and the COPII coat. It is one of 5 proteins constituting the COPII coat, which is involved in anterograde (ER to Golgi) double-membrane transport vesicle formation. First the small GTPase SAR1, activated by and binding to the integral ER membrane protein SEC12, exchanges GDP for GTP and recruits the heterodimer SEC23/24, which in turn recruits the heterotetramer SEC13-SEC31. The polymerization of COPII coat complexes then causes physically the deformation (budding) of the membrane, leading to the creation of a transport vesicle. The COPII complex is dissociated upon SAR1-GTP hydrolysis to SAR1-GDP. SEC23 functions as the SAR1 GTPase activating protein, whose activity is stimulated in the presence of SEC13/31. SEC13 is directly or indirectly required for normal ER membrane and nuclear envelope morphology. It also functions as a component of the nuclear pore complex (NPC). NPC components, collectively referred to as nucleoporins (NUPs), can play the role of both NPC structural components and of docking or interaction partners for transiently associated nuclear transport factors. SEC13 is required for efficient mRNA export from the nucleus to the cytoplasm and for correct nuclear pore biogenesis and distribution. Component of the SEA complex which coats the vacuolar membrane and is involved in intracellular trafficking, autophagy, response to nitrogen starvation, and amino acid biogenesis. The basic repeat unit of a COPII coated vesicle is composed of 5 proteins: the small GTPase SAR1, the heterodimeric SEC23-SEC24 complex, and the heterotetrameric SEC13-SEC31 complex. This repeat unit polymerizes to induce membrane deformation into a transport vesicle. Component of the nuclear pore complex (NPC). NPC constitutes the exclusive means of nucleocytoplasmic transport. NPCs allow the passive diffusion of ions and small molecules and the active, nuclear transport receptor-mediated bidirectional transport of macromolecules such as proteins, RNAs, ribonucleoparticles (RNPs), and ribosomal subunits across the nuclear envelope. Due to its 8-fold rotational symmetry, all subunits are present with 8 copies or multiples thereof. SEC13 is part of the heptameric 0.5 MDa autoassembling NUP84 NPC subcomplex (NUP84, NUP85, NUP120, NUP133, NUP145C, SEC13 and SEH1). Component of the SEA complex composed of at least IML1/SEA1, RTC1/SEA2, MTC5/SEA3, NPR2, NPR3, SEA4, SEC13 and SEH1. Present with 21400 molecules/cell in log phase SD medium. Belongs to the WD repeat SEC13 family.