The early steps in the biosynthesis of Mr 46,000 mannose 6-phosphate-specific receptor (MPR 46) have been studied by in vivo labeling of transfected BHK cells. The acquisition of phosphomannan-binding activity was compared with changes in protein structure and posttranslational modifications of MPR 46. Intramolecular disulfide bonds were formed before MPR 46 acquired a ligand-binding conformation. A conformational change that resulted in increased trypsin resistance, formation of highly immunogenic epitopes and assembly to noncovalently linked homodimers was observed almost simultaneously with the acquisition of ligand-binding activity. MPR 46 was shown to acquire ligand-binding activity before N-linked oligosaccharides were processed to complex-type forms. Maturation of the ligand-binding conformation was observed under conditions where transport to the Golgi was blocked by lowering the temperature to 16 degrees C, or by addition of brefeldin A or dinitrophenol to the medium at 37 degrees C. This suggests that receptor maturation and assembly take place before reaching the Golgi complex. The affinity towards phosphomannan-containing ligands was shown to be similar for the high-mannose and complex-glycosylated forms of MPR 46.
Assembly of the ligand-binding conformation of Mr 46,000 mannose 6-phosphate-specific receptor takes place before reaching the Golgi complex.
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A Hille, A Waheed, K von Figura; Assembly of the ligand-binding conformation of Mr 46,000 mannose 6-phosphate-specific receptor takes place before reaching the Golgi complex.. J Cell Biol 1 April 1990; 110 (4): 963–972. doi: https://doi.org/10.1083/jcb.110.4.963
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