Insulin-containing secretory granules are bound to Myosin Va via Rab27a in a complex of uncertain composition. Myosin Va moves along the cortical actin network (actin at the periphery of the cytoplasm), carrying the granules to the inner surface of the plasma membrane. A beta cell contains about 10 000 secretory granules. Of these, about 1000 are docked at the inner surface of the plasma membrane and a subset of about 100 docked granules form the "readily releasable" pool (granules which are released within about 5 minutes of glucose stimulation). Docking occurs by interaction between EXOC3/Sec6 located on the membrane of the secretory granule and EXOC4/Sec8 located at the plasma membrane. Additional components (EXOC1, EXOC2, EXOC5, EXOC6, EXOC7, EXOC8) form the Exocyst Complex.