Tyrosine sulfation is a trans-Golgi-specific protein modification
The trans-Golgi has been recognized as having a key role in terminal glycosylation and sorting of proteins. Here we show that tyrosine sulfation, a frequent modification of secretory proteins, occurs specifically in the trans-Golgi. The heavy chain of immunoglobulin M (IgM) produced by hybridoma cells was found to contain tyrosine sulfate. This finding allowed the comparison of the state of sulfation of the heavy chain with the state of processing of its N-linked oligosaccharides. First, the pre-trans-Golgi forms of the IgM heavy chain, which lacked galactose and sialic acid, were unsulfated, whereas the trans-Golgi form, identified by the presence of galactose and sialic acid, and the secreted form of the IgM heavy chain were sulfated. Second, the earliest form of the heavy chain detectable by sulfate labeling, as well as the heavy chain sulfated in a cell-free system in the absence of vesicle transport, already contained galactose and sialic acid. Third, sulfate-labeled IgM moved to the cell surface with kinetics identical to those of galactose-labeled IgM. Lastly, IgM labeled with sulfate at 20/sup 0/C was not transported to the cell surface at 20/sup 0/C but reached the cell surface at 37/sup 0/C. The data suggest that within the trans-Golgi, tyrosine sulfation of IgM occurred at least in part after terminal glycosylation and therefore appeared to be the last modification of this constitutively secreted protein before its exit from this compartment. Furthermore, the results establish the covalent modification of amino acid side chains as a novel function of the trans-Golgi.
- Research Organization:
- European Molecular Biology Laboratory, Heidelberg, Germany, F.R.
- OSTI ID:
- 5401339
- Journal Information:
- J. Cell Biol.; (United States), Journal Name: J. Cell Biol.; (United States) Vol. 105; ISSN JCLBA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
BIOLOGICAL FUNCTIONS
CARBOHYDRATES
CARBOXYLIC ACIDS
CELL CONSTITUENTS
DRUGS
FUNCTIONS
GLOBULINS
HYDROXY ACIDS
IMMUNOGLOBULINS
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LIPOTROPIC FACTORS
METABOLISM
METHIONINE
OLIGOSACCHARIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXYGEN COMPOUNDS
PROTEINS
SACCHARIDES
STRUCTURE-ACTIVITY RELATIONSHIPS
SULFATES
SULFUR COMPOUNDS
SULFUR ISOTOPES
TRACER TECHNIQUES
TYROSINE