Two Naturally Occurring α2,6-Sialyltransferase Forms with a Single Amino Acid Change in the Catalytic Domain Differ in Their Catalytic Activity and Proteolytic Processing
| Autor: | Rong Qian, Jiyan Ma, Karen J. Colley, Francisco M. Rausa |
|---|---|
| Rok vydání: | 1997 |
| Předmět: |
Stereochemistry
Golgi Apparatus CHO Cells Biology Endoplasmic Reticulum Biochemistry Catalysis Structure-Activity Relationship symbols.namesake chemistry.chemical_compound Cricetinae Glycosyltransferase Animals Nucleotide RNA Messenger RNA Processing Post-Transcriptional beta-D-Galactoside alpha 2-6-Sialyltransferase Molecular Biology chemistry.chemical_classification COS cells Biological Transport Cell Biology Golgi apparatus Recombinant Proteins Sialyltransferases Cell Compartmentation Rats Sialic acid Amino acid Transport protein Genes chemistry COS Cells symbols biology.protein Glycoprotein Protein Processing Post-Translational |
| Zdroj: | Journal of Biological Chemistry. 272:672-679 |
| ISSN: | 0021-9258 |
| Popis: | The alpha2,6-sialyltransferase (ST) is a Golgi glycosyltransferase that adds sialic acid residues to glycoprotein N-linked oligosaccharides. Here we show that two forms of alpha2,6-sialyltransferase are expressed by the liver and are encoded by two different RNAs that differ by a single nucleotide. The ST tyr possesses a Tyr at amino acid 123, whereas the ST cys possesses a Cys at this position. The ST tyr is more catalytically active than the ST cys; however, both are functional when introduced into tissue culture cells. The proteolytic processing and turnover of the ST tyr and ST cys proteins differ dramatically. The ST cys is retained intact in COS-1 cells, whereas the ST tyr is rapidly cleaved and secreted. Analysis of the N-linked oligosaccharides of these proteins demonstrates that both proteins enter the late Golgi. However, differences in ST tyr and ST cys proteolytic processing may be related to differences in their localization, because ST tyr but not ST cys is expressed at low levels on the cell surface. The possibility that the ST tyr is cleaved in a post-Golgi compartment is supported by the observation that a 20 degrees C temperature block, which stops protein transport in the trans Golgi network, blocks both cleavage and secretion of the ST tyr. |
| Databáze: | OpenAIRE |
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