RRC ID 38805
Author Haraguchi M, Yamashiro S, Furukawa K, Takamiya K, Shiku H, Furukawa K.
Title The effects of the site-directed removal of N-glycosylation sites from beta-1,4-N-acetylgalactosaminyltransferase on its function.
Journal Biochem J
Abstract The amino acid sequence deduced from the cloned human cDNA of beta-1,4-N-acetylgalactosaminyltransferase (GalNAc-T; EC gene predicted three potential sites for N-linked glycosylation. Although many glycosyltransferases isolated contain from 2 to 6 N-glycosylation sites, their significance has not been adequately demonstrated. To clarify the roles of N-glycosylation in GalNAc-T function, we generated a series of mutant cDNAs, in which some or all of the glycosylation recognition sites were eliminated by polymerase chain reaction (PCR)-mediated site-directed mutagenesis. Using transcription/translation in vitro, we confirmed that all potential N-glycosylation sites could be used. Although cell lines transfected with mutant cDNAs showed equivalent levels of GalNAc beta 1-->4(NeuAc alpha 2-->3)Gal beta 1-->4Glc-Cer (GM2) to that of the wild-type, the extracts from mutant cDNA transfectants demonstrated lower enzyme activity than in the wild-type. The decrease in enzyme activity was more evident as the number of deglycosylated sites increased, with about 90% decrease in a totally deglycosylated mutant. The enzyme kinetics analysis revealed no significant change of Km among wild-type and mutant cDNA products. The intracellular localization of GalNAc-T expressed in transfectants with wild-type or mutant cDNAs also showed a similar perinuclear pattern (Golgi pattern). These results suggest that N-linked carbohydrates on GalNAc-T are required for regulating the stability of the enzyme structure.
Volume 312 ( Pt 1)(Pt 1)
Pages 273-80
Published 1995-11-15
DOI 10.1042/bj3120273
PMID 7492324
PMC PMC1136255
MeSH Animals Base Sequence Blotting, Southern CHO Cells Cricetinae G(M2) Ganglioside / biosynthesis Glycosylation Humans Immunohistochemistry Kinetics Mice Molecular Sequence Data Mutagenesis, Site-Directed* N-Acetylgalactosaminyltransferases / chemistry N-Acetylgalactosaminyltransferases / genetics N-Acetylgalactosaminyltransferases / metabolism* Point Mutation Protein Biosynthesis Sequence Analysis Transcription, Genetic Transfection Tumor Cells, Cultured
IF 4.097
Times Cited 51
Human and Animal Cells CHO-K1(RCB0285)