Figure 2.

Vesicle budding and fusion. (1) Coat proteins are recruited to donor membranes, which have a characteristic lipid and protein composition and local curvature. Typically, a membrane-and-cargo-adapter-like layer and a coat-like membrane layer are assembled. Coat proteins and additional components concentrate cargo in the forming bud. (2) Membrane curvature increases and a vesicle neck forms. (3) Vesicle scission results in the release of the cargo-laden vesicle from the donor compartment. (4) Vesicle uncoating occurs, allowing subsequent fusion with the acceptor compartment. Coat proteins are released for recycling. (5) Fusion with the recipient compartment occurs and the release of cargo.