(Quasi‐)Racemic X‐ray Structures of Glycosylated and Non‐Glycosylated Forms of the Chemokine Ser‐CCL1 Prepared by Total Chemical Synthesis |
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| Authors: | Prof. Dr. Ryo Okamoto Dr. Kalyaneswar Mandal Dr. Michael R. Sawaya Prof. Dr. Yasuhiro Kajihara Prof. Dr. Todd O. Yeates Prof. Dr. Stephen B. H. Kent |
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| Affiliation: | 1. Departments of Chemistry: Biochemistry & Molecular Biology, Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637 (USA);2. Current address: Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560‐0043, JAPAN.;3. Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095 (USA);4. Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 5600043 (Japan) |
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| Abstract: | Our goal was to obtain the X‐ray crystal structure of the glycosylated chemokine Ser‐CCL1. Glycoproteins can be hard to crystallize because of the heterogeneity of the oligosaccharide (glycan) moiety. We used glycosylated Ser‐CCL1 that had been prepared by total chemical synthesis as a homogeneous compound containing an N‐linked asialo biantennary nonasaccharide glycan moiety of defined covalent structure. Facile crystal formation occurred from a quasi‐racemic mixture consisting of glycosylated L ‐protein and non‐glycosylated‐D ‐protein, while no crystals were obtained from the glycosylated L ‐protein alone. The structure was solved at a resolution of 2.6–2.1 Å. However, the glycan moiety was disordered: only the N‐linked GlcNAc sugar was well‐defined in the electron density map. A racemic mixture of the protein enantiomers L ‐Ser‐CCL1 and D ‐Ser‐CCL1 was also crystallized, and the structure of the true racemate was solved at a resolution of 2.7–2.15 Å. Superimposition of the structures of the protein moieties of L ‐Ser‐CCL1 and glycosylated‐L ‐Ser‐CCL1 revealed there was no significant alteration of the protein structure by N‐glycosylation. |
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| Keywords: | chemical protein synthesis glycoprotein mirror image proteins quasi‐racemic crystals X‐ray structure |
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