Perilipin is a 62kD constitutively phosphorylated protein that belongs to the PAT (Perilipin/Adipophilin/TIP47) family of molecules. Found primarily in mature adipocytes, perilipin-1 interacts with lipid-coat proteins at the edge of the fat droplet and blocks lipase activity. Upon phosphorylation, perilipin-1 becomes a 65-67kD molecule that likely promotes the dispersion of docking molecules and provides a scaffold for lipase at the lipid droplet surface. Human perilipin-1 is 522aa in length. It contains a lipid droplet targeting region aa233-364 that contains a polyGlu segment aa307-316. Phosphorylation at the N-terminus is necessary for lipase interaction with lipid. One 50-54kD human splice variant (perilipin-B) is reported that shows an 85aa substitution for aa404-522. This apparently interacts with cell membrane triglycerides. Over aa8-145, human perilipin-1/A shares 97aa identity with mouse perilipin-1.