Cloning and expression of a proteoglycan UDP-galactose:beta-xylose beta1,4-galactosyltransferase I. A seventh member of the human beta4-galactosyltransferase gene family.

Abstract

A seventh member of the human beta4-galactosyltransferase family, beta4Gal-T7, was identified by BLAST analysis of expressed sequence tags. The coding region of beta4Gal-T7 depicts a type II transmembrane protein with sequence similarity to beta4-galactosyltransferases, but the sequence was distinct in known motifs and did not contain the cysteine residues conserved in the other six members of the beta4Gal-T family. The genomic organization of beta4Gal-T7 was different from previous beta4Gal-Ts. Expression of beta4Gal-T7 in insect cells showed that the gene product had beta1,4-galactosyltransferase activity with beta-xylosides, and the linkage formed was Galbeta1-4Xyl. Thus, beta4Gal-T7 represents galactosyltransferase I enzyme (xylosylprotein beta1, 4-galactosyltransferase; EC 2.4.1.133), which attaches the first galactose in the proteoglycan linkage region GlcAbeta1-3Galbeta1-3Galbeta1-4Xylbeta1-O-Ser. Sequence analysis of beta4Gal-T7 from a fibroblast cell line of a patient with a progeroid syndrome and signs of the Ehlers-Danlos syndrome, previously shown to exhibit reduced galactosyltransferase I activity (Quentin, E., Gladen, A., Rodén, L., and Kresse, H. (1990) Proc. Natl. Acad. Sci. U. S. A. 87, 1342-1346), revealed two inherited allelic variants, beta4Gal-T7(186D) and beta4Gal-T7(206P), each with a single missense substitution in the putative catalytic domain of the enzyme. beta4Gal-T7(186D) exhibited a 4-fold elevated K(m) for the donor substrate, whereas essentially no activity was demonstrated with beta4Gal-T7(206P). Molecular cloning of beta4Gal-T7 should facilitate general studies of its pathogenic role in progeroid syndromes and connective tissue disorders with affected proteoglycan biosynthesis.

• Authors: R Almeida, S B Levery, U Mandel, H Kresse, T Schwientek, E P Bennett, H Clausen
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 274 Issue 37 Pg. 26165-71 (Sep 10 1999) ISSN: 0021-9258 [Print] United States
• PMID: 10473568 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• DNA, Complementary
• Galactosyltransferases
• UDP-galactose xylose galactosyltransferase

Topics

• Amino Acid Sequence
• Base Sequence
• Cloning, Molecular
• DNA, Complementary
• Galactosyltransferases (chemistry, genetics, metabolism)
• Humans
• Magnetic Resonance Spectroscopy
• Molecular Sequence Data
• Sequence Homology, Amino Acid