cDNA Cloning and Expression of a Novel Human UDP-N-acetyl-α-D-galactosamine
POLYPEPTIDE N-ACETYLGALACTOSAMINYLTRANSFERASE, GalNAc-T3*
- ‡To whom the correspondence should be addressed: School of Dentistry, Nørre Alle 20, DK-2200 Copenhagen N, Denmark. Tel.: 45-3532-6835; Fax: 45-3532-6505.
Abstract
The glycosylation of serine and threonine residues during mucin-type O-linked protein glycosylation is carried out by a family of UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferases (GalNAc-transferase). Previously two members, GalNAc-T1 and −T2, have been isolated and the genes cloned and characterized. Here we report the cDNA cloning and expression of a novel GalNAc-transferase termed GalNAc-T3. The gene was isolated and cloned based on the identification of a GalNAc-transferase motif (61 amino acids) that is shared between GalNAc-T1 and −T2 as well as a homologous Caenorhabditis elegans gene. The cDNA sequence has a 633-amino acid coding region indicating a protein of 72.5 kDa with a type II domain structure. The overall amino acid sequence similarity with GalNAc-T1 and −T2 is approximately 45%; 12 cysteine residues that are shared between GalNAc-T1 and −T2 are also found in GalNAc-T3. GalNAc-T3 was expressed as a soluble protein without the hydrophobic transmembrane domain in insect cells using a Baculo-virus vector, and the expressed GalNAc-transferase activity showed substrate specificity different from that previously reported for GalNAc-T1 and −T2. Northern analysis of human organs revealed a very restricted expression pattern of GalNAc-T3.
Footnotes
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↵* This work was supported by the Danish Medical Research Council, the Danish Natural Science Research Council, the Lundbeck Foundation, Ib Henriksens Foundation, the Gangsted Foundation, the Novo Nordisk Foundation, and the Ingeborg Roikjer's Foundation. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) X92689[GenBank].
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↵1 The abbreviations used are:
- GalNAc-transferase
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UDP-N-acetyl-α-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase
- bp
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base pair(s)
- kb
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kilobase(s)
- PCR
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polymerase chain reaction
- RT
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reverse transcriptase
- pfu
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plaque-forming units
- MTN
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multiple tissue Northern blots
- HIV
-
human immunodeficiency virus.
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↵2 GalNAc-T1 is a GalNAc-transferase originally cloned by Homa et al. (1); GalNAc-T2 is a GalNAc-transferase originally cloned by White et al. (3); and GalNAc-T3 is the GalNAc-transferase cloned in the present paper.
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↵3 E. P. Bennett and H. Clausen, unpublished observations.
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- Received July 5, 1995.
- Revision received April 15, 1996.
- © 1996 by The American Society for Biochemistry and Molecular Biology, Inc.
