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J. Cell Biol.,
Volume 140, Number 5, March 9, 1998 1063-1074
Department of Biochemistry, University of Iowa, Iowa City, Iowa 52242
During each cell cycle, the yeast vacuole actively partitions between mother and daughter cells.
This process requires actin, profilin, an unconventional
myosin (Myo2p), and Vac8p. A mutant yeast strain,
vac8, is defective in vacuole inheritance, specifically, in
early vacuole migration. Vac8p is a 64-kD protein
found on the vacuole membrane, a site consistent with
its role in vacuole inheritance. Both myristoylation and
palmitoylation are required for complete Vac8p localization. Interestingly, whereas myristoylation of Vac8p
is not required for vacuole inheritance, palmitoylation is essential. Thus, palmitoylation appears to play a
more direct role in vacuole inheritance. Most of the
VAC8 sequence encodes 11 armadillo (Arm) repeats.
Arm repeats are thought to mediate protein-protein interactions, and many Arm proteins have multiple functions. This is also true for Vac8p. In addition to its role in early vacuole inheritance, Vac8p is required to target
aminopeptidase I from the cytoplasm to the vacuole.
Mutant analysis demonstrates that Vac8p functions
separately in these two processes. Vac8p cosediments
with actin filaments. Vac8p is related to
-catenin and
plakoglobin, which connect a specific region of the
plasma membrane to the actin cytoskeleton. In analogy, Vac8p may link the vacuole to actin during vacuole
partitioning.
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