FIG. 3.

Hypothetical models describing targeting and transfer of proteins to lipid particles. (A) Budding of a neutral lipid-rich domain from the endoplasmic reticulum is accompanied by association of proteins with the phospholipid monolayer of newly formed lipid particles. According to this model, polypeptides without TM regions would preferentially associate with lipid particles. Nasc-LP, nascent lipid particles. (B) Association of proteins with preexisting lipid particles though a targeting signal on the polypeptide. (C) Transport of proteins to preexisting lipid particles by vesicle (V) flow. LP, lipid particles; ER, endoplasmic reticulum.