Isolation and characterization of the two glycosylation isoforms of low molecular weight mannose 6-phosphate receptor from bovine testis. Effect of carbohydrate components on ligand binding

• Published in: The Journal of biological chemistry 1991-09, Vol.266 (26), p.17621-17630
• Main Authors: MAOMI LI, JOURDIAN, G. W
• Format: Article
• Language: English
• Subjects: alpha-Galactosidase - metabolism; Amino Acids - analysis; Amino Sugars - chemistry; Animals; Biological and medical sciences; Carbohydrate Metabolism; Carbohydrates - analysis; Carbohydrates - chemistry; Cattle; Cell receptors; Cell structures and functions; Centrifugation; Chromatography, Affinity; Electrophoresis, Polyacrylamide Gel; Fundamental and applied biological sciences. Psychology; Glycosylation; insulin-like growth factor II; Lectins; Ligands; Male; Mannosephosphates - metabolism; membrane proteins; Mice; Miscellaneous; Molecular and cellular biology; Molecular Weight; Polysaccharides - chemistry; Receptor, IGF Type 2; Receptors, Cell Surface - chemistry; Receptors, Cell Surface - isolation & purification; Receptors, Cell Surface - metabolism; Sialic Acids - chemistry; Testis - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(19)47417-6

Low molecular weight mannose 6-phosphate receptor from bovine testis exhibits two isoforms on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with Mr values of 45,000 (MPR-2A) and 41,000 (MPR-2B), respectively. Each isoform was purified to near homogeneity by the sequential application of differential centrifugation and affinity chromatography. The isoforms contain a common polypeptide core, but differ in their carbohydrate content. Treatment with specific endoglycosidases demonstrated that each isoform contains two high mannose and/or hybrid and two complex N-linked oligosaccharide chains. The results obtained from treatment of each isoform with endo-beta-galactosidase and neuraminidases and from lectin affinity chromatography reveal that MPR-2A contains a linear polylactosamine sequence(s) comprised of approximately 5 lactosamine units. A majority of the outer branches of the complex chains associated with MPR-2A are terminated with sialic acid residues. In contrast, MPR-2B lacks a polylactosamine sequence and a majority of the outer branches of the complex chains are terminated with galactose residues. MPR-2A exhibited a lower affinity than MPR-2B for mannose 6-phosphate-containing ligands. Treatment of MPR-2A with endo-beta-galactosidase and/or neuraminidases followed by affinity chromatography revealed that polylactosamine and sialic acid residues impair the ability of MPR-2A to bind ligands.