Golgi Retention Mechanism of 
-1,4-Galactosyltransferase
MEMBRANE-SPANNING DOMAIN-DEPENDENT HOMODIMERIZATION AND ASSOCIATION WITH α- AND β-TUBULINS (*)
- ¶To whom correspondence should be addressed: La Jolla Cancer Research Foundation, 10901 N. Torrey Pines Rd., La Jolla, CA 92037.
Abstract
Recent studies on proteins residing in the Golgi complex revealed that the membrane-spanning domain of these proteins are
largely responsible for their retention in the Golgi complex. We show here that β-1,4-galactosyltransferase (GT) forms homodimers
and large oligomers in vivo, and the formation of the homodimers is dependent on cysteine and histidine residues within the transmembrane domain. Double
mutations of these residues, Cys
Ser and His
Leu, abolish homodimerization and simultaneously reduce the Golgi retention. Co-immunoprecipitation of GT and various GT
chimeras with anti-GT and anti-reporter molecule antibodies revealed that large aggregates of GT are associated with α- and
β-tubulins and also with other cellular proteins. This association between tubulins and GT suggests a supportive role of the
cytoskeleton in the Golgi retention mechanism.
Footnotes
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↵§ Supported by a research fellowship from the Uehara Memorial Foundation (Tokyo, Japan). Present address: Dept. of Cell Differentiation, Institute of Molecular Embryology and Genetics, Kumamoto University School of Medicine, 2-2-1, Honjo, Kumamoto 860, Japan.
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↵* This work was supported in part by Grant R01-DK37016 from the National Institutes of Health. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵1 The abbreviations used are:
- ER
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endoplasmic reticulum
- GT
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UDP-galactose:β-D-N-acetylglucosaminide β-1,4-galactosyltransferase
- TfR
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transferrin receptor
- CHO
-
Chinese hamster ovary
- PAGE
-
polyacrylamide gel electrophoresis
- endo H
-
endo-β-N-acetylglucosaminidase H
- PVDF
-
polyvinylidene difluoride.
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↵2N. Yamaguchi and M. N. Fukuda, unpublished data.
- © 1995 by The American Society for Biochemistry and Molecular Biology, Inc.
