ISSN:
1573-4986
Keywords:
glycosyltransferase
;
Golgi
;
epitope tagging
;
glycosphingolipid
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Cloned human β1,4N-acetylgalactosaminyltransferase (GalNAcT) catalyses the synthesis of the glycosphingolipids GM2, GD2, and gangliotriosylceramide. To determine the subcellular location of this enzyme and whether it exists in intermolecular disulfide bonded species, we stably transfected Chinese hamster ovary (CHO) cells with three myc epitope-tagged forms of the GalNAcT gene: the native enzyme; the lumenal domain of GalNAcT fused to the cytoplasmic and transmembrane domains ofN-acetylglucosaminyltransferase I (GNT); and the transmembrane and lumenal domains of GalNAcT fused to the cytoplasmic domain of the Iip33 form of human invariant chain in order to retain the enzyme in the endoplasmic reticulum (ER). Immunoelectron microscopic analysis with anti-myc revealed that GalNAcT/myc was present throughout the Golgi stack, the GNT/GalNAcT/myc form was restricted primarily to the medial Golgi cisternae, and the Iip33/GalNAcT/myc form was restricted to the ER. Cells transfected with each of the three constructs contained high levels of GM2 synthase activityin vitro, but only the GalNAcT/myc form and the GNT/GalNAcT/myc forms were able to synthesize the GM2 productin vivo. The enzyme produced by all three constructs was present in the transfected cells in a disulfide bonded form having a molecular size consistent with that of a homodimer or higher aggregate.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00731496
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