High Quality Content by WIKIPEDIA articles! Vacuolar protein sorting-associated protein 33A is a protein that in humans is encoded by the VPS33A gene. Vesicle mediated protein sorting plays an important role in segregation of intracellular molecules into distinct organelles. Genetic studies in yeast have identified more than 40 vacuolar protein sorting (VPS) genes involved in vesicle transport to vacuoles. This gene is a member of the Sec-1 domain family, and it encodes a protein similar to the yeast class C Vps33 protein.