Title :
O-N-acetyl-D-glucosamine moiety on discrete
peptide of multiple
protein 4.1 isoforms regulated by alternative pathways
Abstract :
- Erythrocyte protein 4.1 is a cytoplasmic protein that possesses a protein-saccharide modification structure, an O-N-acetyl-D-glucosamine (GlcNAc) moiety.
- We determined the amino acid sequence of the proteolytic fragment containing the O-GlcNAc moiety after labeling the saccharide with [3H]galactose in the presence of bovine milk galactosyltransferase
- Glycosylation appears to occur on one or more serine or threonine residues in the following sequence: Thr-Ala-Gln-Thr-Ile-Thr-Ser-Glu-Thr-Pro-Ser-Ser-Thr-Thr-Thr-Thr-Gln-Ile-Thr-Lys
- This sequence corresponds to the carboxyl-terminal half of the 34-amino acid peptide in the 22/24-kDa carboxyl-terminal domain of protein 4.1 , which is one of the discrete peptides regulated by alternative RNA splicing
- Multiple protein 4.1 isoforms in erythroid and nonerythroid cells including major components of erythrocyte membrane proteins , 4.1a and 4.1b, appear to contain this sequence since most immunochemically reactive proteins were labeled with [3H]galactose, with the exception of several variant polypeptides
- These results appear to suggest the functional or biological significance of the O-GlcNAc linkage in protein 4.1