Mannose 6-phosphate-specific receptor is a transmembrane protein with a C-terminal extension oriented towards the cytosol.
The portion of the mannose 6-phosphate receptor (nominal Mr 180000 under nonreducing conditions) protruding at the external side of the plasma membrane of fibroblasts and HepG2 cells is susceptible to trypsin. A series of membrane-bound fragments smaller in Mr by 20000-65000 is obtained after incubation of cells with trypsin. When membranes from fibroblasts and HepG2 cells are incubated with trypsin or Staphylococcus aureus proteinase, the receptor is degraded to a single membrane-bound product smaller in Mr by about 9000. In the presence of 0.1% Triton X-100 extensive degradation of the receptor by trypsin is observed. Furthermore, the receptor in isolated membranes is sensitive to carboxypeptidase Y, which causes a decrease in Mr by about 5000 and 9000 in the absence or presence of detergent, respectively. Mannose 6-phosphate receptor appears to be a transmembrane protein with multiple trypsin-sensitive sites within its larger external (luminal) and smaller C-terminal (cytosolic) portions of the molecule.
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D000818:Animals; D002268:Carboxypeptidases / Q000494:pharmacology; D002352:Carrier Proteins / Q000276:immunology / Q000378:metabolism* / Q000494:pharmacology; D002460:Cell Line; D011232:Chemical Precipitation; D003600:Cytosol / Q000378:metabolism; D010450:Endopeptidases / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D008114:Liver Neoplasms, Experimental / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D017527:Receptor, IGF Type 2; D012697:Serine Endopeptidases; D014357:Trypsin / Q000494:pharmacology
D002352:Carrier Proteins; D008565:Membrane Proteins; D017527:Receptor, IGF Type 2; D002268:Carboxypeptidases; D010450:Endopeptidases; C022633:serine carboxypeptidase; D012697:Serine Endopeptidases; C028344:glutamyl endopeptidase; D014357:Trypsin