Effects of Glycosylation on the Structure and Dynamics of Eel Calcitonin in Micelles and Lipid Bilayers Determined by Nuclear Magnetic Resonance Spectroscopy

• Published in: Biochemistry (Easton) 1999-06, Vol.38 (26), p.8377-8384
• Main Authors: Hashimoto, Yasuhiro, Toma, Kazunori, Nishikido, Joji, Yamamoto, Keizo, Haneda, Katsuji, Inazu, Toshiyuki, Valentine, Kathleen G, Opella, Stanley J
• Format: Article
• Language: English
• Subjects: Acetylglucosamine - chemistry; Amino Acid Sequence; Anguilla; Anguilliformes; Animals; Brackish; Calcitonin - chemistry; Calcitonin - metabolism; Carbohydrate Conformation; Carbohydrate Sequence; Crystallography, X-Ray; Eels; Freshwater; Glycosylation; Lipid Bilayers - chemistry; Lipid Bilayers - metabolism; Marine; Micelles; Molecular Sequence Data; Nuclear Magnetic Resonance, Biomolecular; Peptide Fragments - chemistry; Peptide Fragments - metabolism; Protein Structure, Secondary; Structure-Activity Relationship; Thermodynamics
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi983018j

The three-dimensional structures of eel calcitonin (CT) and two glycosylated CT derivatives, [Asn(GlcNAc)3]-CT (CT-GlcNAc) and [Asn(Man6-GlcNAc2)3]-CT (CT-M6), in micelles were determined by solution NMR spectroscopy. The topologies of these peptides associated with oriented lipid bilayers were determined with solid-state NMR. All of the peptides were found to have an identical conformation in micelles characterized by an amphipathic α-helix consisting of residues Ser5 through Leu19 followed by an unstructured region at the C-terminus. The overall conformation of the peptide moiety was not affected by the glycosylation. Nevertheless, comparison of the relative exchange rates of the Leu12 amide proton might suggest the possibility that fluctuations of the α-helix are reduced by glycosylation. The presence of NOEs between the carbohydrate and the peptide moieties of CT-GlcNAc and CT-M6 and the amide proton chemical shift data suggested that the carbohydrate interacted with the peptide, and this might account for the conformational stabilization of the α-helix. Both the unmodified CT and the glycosylated CT were found to have orientations with their helix axes parallel to the plane of the lipid bilayers by solid-state NMR spectroscopy.