Heterogeneous glycosylation of murine transferrin receptor subunits

The N-linked glycosylation of the murine receptor for transferrin has been investigated. Previously we have found that purified receptors appear as two bands after sodium dodecyl sulfate/polyacrylamide gel electrophoresis and Coomassie blue staining [van Driel, I.R., Stearne, P.A., Grego, B., Simpson, R.J. and Goding, J.W. (1984) J. Immunol. 133, 3220-3224]. In the current report we show that the two bands are due to different glycosylation of individual receptor molecules. The receptors have three asparagines to which N-linked glycans can be added, but only two sites are glycosylated in all receptors. The level of glycosylation of the third site varies depending on cell line or tissue. Limited endoglycosidase digestion of mature receptors indicates that differential glycosylation probably occurs at only one particular asparagine residue. Possible mechanisms that could result in such a glycosylation pattern are discussed.