Analyzing Conformation of Fusion Protein on Bivalent Single-Chain Antibody with (Gly4Ser)n

Abstract-scFv (single-chain Fv fragment)is the gene engineered antibody employed widely in at present. Recently there have been some progress on colorectal cancer diagnosis and treatment-oriented with scFv as carrier, but it is differential on affinity and anti-tumor activity of scFv with that of derived factor. Proper linker could make scFv have more suitable biological activity on clinical application. So it becomes a key step that how to choose and design a proper linker. In this work, the (Gly4Ser)n is used as the linker to connect VH and VL separately (n=0,1,2,3,4,5,6,7,8,9). and the 3D structure of corresponding scFv is reconstructed by homology modeling. The End-End distance of scFy protein with different linker (G4S)n, which 3D structure coordinate system are normalized, are compared to evaluate the effect of linker length to VH and VL. In molecular biology experiment, ND-1scFv-n are expressed and analyzed with n=1,3,5,7,9, their biologic activity active are consistent with what estimated by End-End distance. So the index to estimate biologic activity of scFv with its End-End distance is presented and could be helpful to further understand the relationship between the spatial structure of single-chain antibody and the physical and chemical properties.