core trisaccharide of an N-linked glycoprotein intrinsically accelerates folding and enhances stability

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 106; no. 9; pp. 3131 - 3136
• Main Authors: Hanson, Sarah R, Culyba, Elizabeth K, Hsu, Tsui-Ling, Wong, Chi-Huey, Kelly, Jeffery W, Powers, Evan T
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 03.03.2009; National Acad Sciences
• Subjects: Amino acids; Animals; Biochemistry; Biological Sciences; CD2 Antigens - chemistry; CD2 Antigens - genetics; CD2 Antigens - metabolism; Cells; Circular Dichroism; Free energy; Glycoproteins; Glycoproteins - chemistry; Glycoproteins - metabolism; Glycosylation; Humans; Immune system; Kinetics; Models, Molecular; Mutation - genetics; Oligosaccharides; Physical Sciences; Polysaccharides; Protein Folding; Protein Stability; Protein Structure, Tertiary; Rats; Renovations; Surface areas; Thermodynamics; Trisaccharides - chemistry; Trisaccharides - metabolism
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0810318105

The folding energetics of the mono-N-glycosylated adhesion domain of the human immune cell receptor cluster of differentiation 2 (hCD2ad) were studied systematically to understand the influence of the N-glycan on the folding energy landscape. Fully elaborated N-glycan structures accelerate folding by 4-fold and stabilize the β-sandwich structure by 3.1 kcal/mol, relative to the nonglycosylated protein. The N-glycan's first saccharide unit accounts for the entire acceleration of folding and for 2/3 of the native state stabilization. The remaining third of the stabilization is derived from the next 2 saccharide units. Thus, the conserved N-linked triose core, ManGlcNAc₂, improves both the kinetics and the thermodynamics of protein folding. The native state stabilization and decreased activation barrier for folding conferred by N-glycosylation provide a powerful and potentially general mechanism for enhancing folding in the secretory pathway.