Title : Transmembrane topology of
PiT-2 , a phosphate transporter-retrovirus
receptor
Abstract :
- PiT-1 and PiT-2 are related multiple transmembrane proteins which function as sodium-dependent phosphate transporters and as the cell receptors of several oncoretroviruses
- Two copies of a homology domain that is found in distantly related species assign these proteins to a large family of phosphate transporters
- A current membrane topology model of PiT-1 and PiT-2 predicts 10 transmembrane domains
- However, the validity of this model has not been addressed experimentally
- We addressed this issue by a comprehensive study of human PiT-2
- Evidence was obtained for glycosylation of asparagine 81
- Epitope tagging showed that the N- and C-terminal extremities are extracellular
- The orientation of C-terminal-truncation mutants expressed in cell-free translation assays and incorporated into microsomal membranes was examined by immunoprecipitation
- Data were interpreted with respect to previous knowledge about retrovirus binding sites , to the existence of repeated homology domains , and to predictions made in family members
- A model in which PiT-2 has 12 transmembrane domains and extracellular N- and C-terminal extremities is proposed
- This model, which differs significantly from previous predictions about PiT-2 topology, may be useful for further investigations of PiT-2 interactions with other proteins and for the understanding of PiT-2 transporter and virus receptor functions
Output (sent_index, trigger,
protein,
sugar,
site):
- 6. glycosylation, , -, -, asparagine 81
Output(Part-Of) (sent_index,
protein,
site):
*Output_Site_Fusion* (sent_index,
protein,
sugar,
site):
- 6. PiT-2, -, asparagine 81