Crystal structure of streptavidin mutant with low immunogenicity

We previously created a low-immunogenic core streptavidin mutant No. 314 (LISA-314) by replacing six amino-acid residues for use as a delivery tool for an antibody multistep pre-targeting process (Yumura et al., Protein Sci., 22, 213-221, 2013). Here, we performed high-resolution X-ray structural analyses of LISA-314 and wild-type streptavidin to investigate the effect of substitutions on the protein function and the three-dimensional structure. LISA-314 forms a tetramer in the same manner as wild-type streptavidin. The binding mode of d-biotin in LISA-314 is also completely identical to that in wild-type streptavidin, and conformational changes were observed mostly at the side chains of substituted sites. Any large conformational changes corresponding to the reduction of B factors around the substituted sites were not observed. These results demonstrated the LISA-314 acquired low immunogenicity without losing structural properties of original wild-type streptavidin.