Title : Processing of N-linked oligosaccharide depends on its location in the anion exchanger,
AE1 , membrane
glycoprotein
Abstract :
- The human erythrocyte anion exchanger ( AE)1 (Band 3) contains a single complex N-linked oligosaccharide that is attached to Asn(642) in the fourth extracellular loop of this polytopic membrane protein , while other isoforms ( AE2 , AE3 and trout AE1 ) are N-glycosylated on the preceding extracellular loop
- Human AE1 expressed in transfected human embryonic kidney ( HEK )-293 or COS-7 cells contained a high-mannose oligosaccharide
- The lack of oligosaccharide processing was not due to retention of AE1 in the endoplasmic reticulum since biotinylation assays showed that approx
- 30% of the protein was expressed at the cell surface
- Moving the N-glycosylation site to the preceding extracellular loop in an AE1 glycosylation mutant ( N555 ) resulted in processing of the oligosaccharide and production of a complex form of AE1
- A double N-glycosylation mutant (N555/N642) contained both a high-mannose and a complex oligosaccharide chain
- The complex form of the N555 mutant could be biotinylated showing that this form of the glycoprotein was at the cell surface
- Pulse-chase experiments showed that the N555 mutant was efficiently converted from a high-mannose to a complex oligosaccharide with a half-time of approx
- 4 h, which reflected the time course of trafficking of AE1 from the endoplasmic reticulum to the plasma membrane
- The turnover of the complex form of the N555 mutant occurred with a half-life of approx
- 15 h
- The results show that the oligosaccharide attached to the endogenous site in extracellular loop 4 in human AE1 is not processed in HEK-293 or COS-7 cells, while the oligosaccharide attached to the preceding loop is converted into the complex form
Output (sent_index, trigger,
protein,
sugar,
site):
- 0. glycoprotein, , glycoprotein, -, -
- 1. N-glycosylated, , AE2, -, -
- 1. N-glycosylated, , AE3, -, -
- 1. N-glycosylated, , isoforms, -, -
- 1. attached, , -, a single complex N-linked oligosaccharide, Asn(642)
- 12. attached, , -, the oligosaccharide, site
- 2. contained, , Human AE1, a high-mannose oligosaccharide, -
- 5. N-glycosylation, , -, -, site
- 7. glycoprotein, , form of the glycoprotein, -, -
Output(Part-Of) (sent_index,
protein,
site):
- 12. AE1, site
- 5. AE1, N555
*Output_Site_Fusion* (sent_index,
protein,
sugar,
site):
- 1. AE1, a single complex N-linked oligosaccharide, Asn(642)