Biogenesis of the Vacuole in Saccharomyces cerevisiae

Abstract

Publisher Summary This chapter describes vacuolar biogenesis in Saccharomyces cerevisiae. It discusses the biosynthesis of endogenous vacuolar proteins, the intracellular routes taken by proteins that are degraded in the vacuole, and the assembly of the vacuolar H+-ATPase. Trafficking of various proteins to the vacuole occurs through several, apparently distinct pathways. These pathways, which converge at or in the vacuole, define a central aspect of the overall vacuolar biogenesis. The chapter also describes the isolation and characterization of several classes of mutants with defects in vacuolar protein sorting, vacuolar assembly, and vacuolar segregation. The characterization of these mutants and the wild-type genes affected in these strains provide clues about the molecular activities required for assembly of this complex organelle. Vacuolar biogenesis not only involves delivery of proteins to the vacuole but also segregation of the organelle to buds during daughter-cell development. The soluble vacuolar glycoproteins possess targeting information within their primary amino-acid sequences that specify interaction with active vacuolar sorting machinery; missorted soluble precursors are secreted at the cell surface through the late stages of the secretory pathway. The soluble vacuolar glycoprotein carboxypeptidase Y (CPY) is considered the best-characterized vacuolar protein in yeast, as it provides a typical example of a soluble vacuolar protein that traverses the secretory pathway during its biosynthesis and delivery to the vacuole.