CCL-1 is a member of chemokine family and naturally N-glycosylated. CCL-1 plays important function in chemotaxis and apoptosis; however, the function of its N-glycan is poorly understood. In 2014, the Okamoto and Kent group reported chemical synthesis of homogeneous N-glycosylated CCL1 and Ser-CCL1 for investigation of biological activity.[27a] Although traditional Fmoc SPPS could not produce glycopeptide thioester, the use of diaminobenzoic acid (Dbz) as a linker could solve this problem and give glycopeptide-Nbz 76 for NCL. The convergent NCL using three segments 75-77 afford full-length glycosylated CCL-1 79 smoothly (Fig 8: Synthetic strategy of the total synthesis of CCL1 having a biantennary oligosaccharide). Following the same protocol, non-glycosylated CCL1, glycosylated and non-glycosylated Ser-CCL1 were also synthesized efficiently. With four synthetic (glyco)proteins in hand, their biological activity was tested by a chemotaxis assay using CCR8-transfected cell line for the elucidation of N-glycan function. According to the result, intriguingly, N-glycosylated CCL1 showed decreased chemotaxis activity compared with non-glycosylated CCL1, which indicate that N-glycosylation might affect other aspect of CCL1 biofunctions.

The Okamoto and Kent group demonstrated very interesting glycoprotein crystallization. Usually, glycans flactuate and therefore this fluctuation interfere glycoprotein crystallization. The Kent group demonstrated the successful racemic crystallization in many examples. OKamoto and Kent examined crystallization with L-glycoprotein and its counter non-glycosylated D-protein.The Kent and Okamoto sucseeded in the crystallization of the first synthetic glycoprotein. The data clearly suggested chemical synthesis indeed give homogeneous glycoprotein without racemization of individual amino acid.[27b]

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