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Tyrosine sulfation is a trans-Golgi-specific protein modification
1Cell Biology Program, European Molecular Biology Laboratory, Heidelberg, Federal Republic of Germany.
The Journal of Cell Biology
|December 1, 1987
Summary
Tyrosine sulfation, a protein modification, occurs in the trans-Golgi. This study shows tyrosine sulfation of immunoglobulin M (IgM) happens after terminal glycosylation, marking it as a late step in protein processing.
Area of Science:
- Cell Biology
- Protein Biochemistry
- Molecular Biology
Background:
- The trans-Golgi network (TGN) is crucial for protein modification and sorting.
- Tyrosine sulfation is a common post-translational modification of secretory proteins.
Purpose of the Study:
- To investigate the precise location and timing of tyrosine sulfation within the secretory pathway.
- To determine the relationship between tyrosine sulfation and N-linked oligosaccharide processing.
Main Methods:
- Utilized hybridoma cells producing immunoglobulin M (IgM).
- Employed sulfate and galactose labeling techniques.
- Compared sulfation status with N-linked oligosaccharide processing stages.
- Investigated protein transport kinetics at different temperatures.
Main Results:
- Tyrosine sulfation of IgM heavy chain was detected specifically in the trans-Golgi.
- Sulfation occurred after terminal glycosylation, indicated by the presence of galactose and sialic acid.
- Sulfation and terminal glycosylation followed identical transport kinetics.
- Temperature-dependent transport studies revealed sulfation precedes cell surface arrival.
Conclusions:
- Tyrosine sulfation of secretory proteins, exemplified by IgM, is a novel function of the trans-Golgi.
- This modification occurs late in the secretory pathway, potentially after terminal glycosylation.
- The trans-Golgi is a key site for diverse protein modifications, including amino acid side chain alterations.