cDNA cloning and expression of a family of UDP-N-acetyl-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase sequence homologs from Caenorhabditis elegans

J Biol Chem. 1998 Apr 3;273(14):8268-77. doi: 10.1074/jbc.273.14.8268.

Abstract

The initiation of mucin-type O-glycosylation is catalyzed by a family of UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferases (ppGaNTase) (EC 2.4.1.41). By screening two mixed-stage Caenorhabditis elegans cDNA libraries, a total of 11 distinct sequence homologs of the ppGaNTase gene family were cloned, sequenced, and expressed as truncated recombinant proteins (gly-3, gly-4, gly-5a, gly-5b, gly-5c, gly-6a, gly-6b, gly-6c, gly-7, gly-8, and gly-9). All clones encoded type II membrane proteins that shared 60-80% amino acid sequence similarity with the catalytic domain of mammalian ppGaNTase enzymes. Two sets of cDNA clones (gly-5 and gly-6) contained variants that appeared to be produced by alternative message processing. gly-6c contained a reading frameshift and premature termination codon in the C-terminal lectin-like domain found in most other ppGaNTase proteins, and a second clone (gly-8) lacked the typical C-terminal region completely. Homogenates of nematodes and immunopurified preparations of the recombinant GLY proteins demonstrated that worms express functional ppGaNTase enzymes (GLY-3, GLY-4, GLY-5A, GLY-5B, and GLY-5C), which can O-glycosylate mammalian apomucin peptide sequences in vitro. In addition to demonstrating the existence of ppGaNTase enzymes in a nematode organism, the substantial diversity of these isoforms in C. elegans suggests that mucin O-glycosylation is catalyzed by a complex gene family, which is conserved among evolutionary-distinct organisms.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Caenorhabditis elegans / enzymology
  • Caenorhabditis elegans / genetics*
  • Cloning, Molecular
  • DNA, Complementary / analysis
  • DNA, Complementary / genetics*
  • Molecular Sequence Data
  • N-Acetylgalactosaminyltransferases / genetics*
  • N-Acetylgalactosaminyltransferases / metabolism
  • Polypeptide N-acetylgalactosaminyltransferase
  • Sequence Alignment
  • Sequence Homology, Amino Acid

Substances

  • DNA, Complementary
  • N-Acetylgalactosaminyltransferases

Associated data

  • GENBANK/AF031833
  • GENBANK/AF031834
  • GENBANK/AF031835
  • GENBANK/AF031836
  • GENBANK/AF031837
  • GENBANK/AF031838
  • GENBANK/AF031839
  • GENBANK/AF031840
  • GENBANK/AF031841
  • GENBANK/AF031842
  • GENBANK/AF031843