Once AP-1 is recruited to the trans-Golgi Network membrane the complex of functional vesicle building proteins is joined by the cargo that will be within that vesicle. As with other types of vesicles the cargo itself is part of the vesicle development. Here the cargo is destined for the lysosome membrane. It is at this stage that a specific Synaptobrevin (Vamp) molecule also joins the complex. It should be noted that only certain Vamp molecules will be found with specific cargo molecules on the newly forming vesicles. However here we represent this reaction in bulk, without specific Vamp and cargo molecule pairings.