Glycosylation beyond the Asn78-linked GlcNAc residue has a significant enhancing effect on the stability of the α subunit of human chorionic gonadotropin

The effects of glycosylation beyond the Asn-linked GlcNAc residues on the stability of the α subunit of human chorionic gonadotropin are investigated using enzymatic deglycosylation and NMR spectroscopy. Comparison of thermal denaturation profiles of both the intact α subunit and the α subunit carrying only GlcNAc monomers at both Asn52 and Asn78 established a small but significant decrease in thermal stability of the deglycosylated form. Since there is no secondary structure around Asn52 in the free subunit these results demonstrate that glycosylation beyond the Asn78-linked GlcNAc residue enhances the thermal stability of the α subunit of hCG. This feature has implications for understanding the effect of glycosylation on protein stabilization in general.