Vesicular transport.

The minimal requirements for COP I and COP II vesicle formation from liposomes are the small GTPases Arf1 and Sar1, GTP and the coat complexes themselves. Coat-nucleating factors including specific GTP-GDP exchange factors, SNAREs and other cargo molecules are likely to determine the site of vesicle formation. Tethering mediated by long rod-like coiled-coil proteins precedes docking of vesicles with their target membrane and contributes to specific recognition of this membrane. NSF/Sec18p acts prior to membrane fusion to prime specific SNARE complexes for docking of vesicles with their targets, while the SNAREs are likely to be the minimal membrane-fusion machinery.