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Molecular and Cellular Biology, December 2001, p. 7981-7994, Vol. 21, No. 23
Cell Biology and Metabolism Branch, National
Institute of Child Health and Human Development, National
Institutes of Health, Bethesda, Maryland 20892-5430
Received 4 June 2001/Returned for modification 27 June
2001/Accepted 4 September 2001
The GGAs (Golgi-localized, gamma-ear-containing, ARF-binding
proteins) are a family of multidomain adaptor proteins involved in
protein sorting at the trans-Golgi network of eukaryotic
cells. Here we present results from a functional characterization of the two Saccharomyces cerevisiae GGAs, Gga1p and Gga2p.
We show that deletion of both GGA genes causes defects in sorting of
carboxypeptidase Y (CPY) and proteinase A to the vacuole, vacuolar
morphology, and maturation of
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.23.7981-7994.2001
Structural Requirements for Function of Yeast GGAs in Vacuolar
Protein Sorting,
-Factor Maturation, and Interactions with
Clathrin
-factor. A structure-function analysis
reveals a requirement of the VHS, GAT, and hinge for function, while
the GAE domain is less important. We identify putative clathrin-binding motifs in the hinge domain of both yeast GGAs. These motifs are shown
to mediate clathrin binding in vitro. While mutation of these motifs
alone does not block function of the GGAs in vivo, combining these
mutations with truncations of the hinge and GAE domains diminishes
function, suggesting functional cooperation between different
clathrin-binding elements. Thus, these observations demonstrate that
the yeast GGAs play important roles in the CPY pathway, vacuole
biogenesis, and
-factor maturation and identify structural
determinants that are critical for these functions.
*
Corresponding author. Mailing address: CBMB, NICHD,
National Institutes of Health, Bldg. 18T, Room 101, 18 Library Dr. MSC 5430, Bethesda, MD 20892-5430. Phone: (301) 496-6368. Fax: (301) 402-0078. E-mail: juan{at}helix.nih.gov.
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