O-glycosylation in Toxoplasma gondii: identification and analysis of a family of UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferases.
The initiation of mucin-type O-glycosylation is catalysed by a family of UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferases (EC 2.4.1.41). These enzymes are responsible for the transfer of N-acetylgalactosamine from the nucleotide sugar donor, UDP-GalNAc, to the hydroxyl group on specific serine or threonine residues in acceptor proteins. By screening a Toxoplasma gondii cDNA library, three distinct isoforms of the ppGalNAc-T gene family were cloned. Two additional isoforms were identified and partially cloned following analysis of the T. gondii genome sequence database. All of the cloned and identified ppGalNAc-T's are type II membrane proteins that share up to 50% amino acid sequence identity within the conserved catalytic domain. They each contain an N-terminal cytoplasmic domain, a hydrophobic transmembrane domain, and a lumenal domain; the latter consists of stem, catalytic, and lectin-like domains. Moreover, each of this ppGalNAc-T's contains important sequence motifs that are typical for this class of glycosyltransferases. These include a glycosyltransferase 1 motif containing the DXH sequence, a Gal/GalNAc-T motif, and the CLD and QXW sequence motifs located in alpha-, beta-, and gamma-repeats present within the lectin-like domain. The coding regions of T. gondii ppGalNAc-T1, -T2, and -T3 reside in multiple exons ranging in number from 6 to 10. Our results demonstrate that mucin-type O-glycosylation in T. gondii is catalysed by a multimember gene family, which is evolutionarily conserved from single-celled eukaryotes through nematodes and insects up to mammals. Taken together, this information creates the basis for future studies of the function of the ppGalNAc-T gene family in the pathobiology of this apicomplexan parasite.
Stwora-Wojczyk
Magdalena M
MM
Department of Genetics, Center for Tropical and Emerging Global Diseases, University of Georgia, 422 Biological Sciences Building, Athens, GA 30602, USA.
Kissinger
Jessica C
JC
Spitalnik
Steven L
SL
Wojczyk
Boguslaw S
BS
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary / Q000235:genetics; D016054:DNA, Protozoan / Q000235:genetics; D017125:Genes, Protozoan; D006031:Glycosylation; D008969:Molecular Sequence Data; D017350:N-Acetylgalactosaminyltransferases / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D016415:Sequence Alignment; D014122:Toxoplasma / Q000201:enzymology* / Q000235:genetics; D014536:Uridine Diphosphate N-Acetylgalactosamine / Q000235:genetics / Q000378:metabolism*; D000097763:Polypeptide N-acetylgalactosaminyltransferase
D018076:DNA, Complementary; D016054:DNA, Protozoan; D017350:N-Acetylgalactosaminyltransferases; D014536:Uridine Diphosphate N-Acetylgalactosamine; D000097763:Polypeptide N-acetylgalactosaminyltransferase