Fig. 1. His3-CPS is a reporter for mutations that block the MVB pathway. Schematic diagram of His3-CPS sorting in wild-type cells (A) and in mutant cells defective in either MVB cargo selection or MVB vesicle formation (B). (C) The growth of wild-type cells and a representative class E vps mutant, vps4, that have been streaked onto medium lacking supplemental histidine.