This small Sec3 C-terminal domain family is based around the fission yeast protein, and is rather shorter than the budding yeast/vertebrate domain Sec3_C, family. Pfam:PF09763. In fact it is only this coiled-coil region that they carry in common. The full length fission yeast, UniProtKB:Q10324, protein Sec3 is redundant with Exo70 for viability and for the localisation of other exocyst subunits, suggesting that these components act as exocyst tethers at the plasma membrane. Sec3, Exo70 and Sec5 are transported by the myosin V Myo52 along actin cables. The exocyst holo-complex, including Sec3 and Exo70, is present on exocytic vesicles, which can reach cell poles by either myosin-driven transport or random walk [1].

1: Fission yeast sec3 and exo70 are transported on actin cables and localize the exocyst complex to cell poles. Bendezu FO, Vincenzetti V, Martin SG; PLoS One. 2012;7:e40248. PMID:22768263