Mutational and gene fusion studies have identified localization signals that target proteins to the yeast lysosome-like vacuole. Genetic analyses have also identified groups of genes (VPS and PEP) whose products are required for recognition of these signals, and sorting and transport of proteins to the vacuole. One of the components involved in protein sorting has been shown to be the vacuolar H+-ATPase, presumably via its role in vacuolar acidification.