5jii

Publication Abstract from PubMed

The crystallizable fragment (Fc) of the immunoglobulin class G (IgG) is an attractive scaffold for the design of novel therapeutics. Upon engineering the C-terminal loops in the CH3 domains, Fcabs (Fc domain with antigen-binding sites) can be designed. We present the first crystal structures of Fcabs, i.e., of the HER2-binding clone H10-03-6 having the AB and EF loop engineered and the stabilized version STAB19 derived by directed evolution. Comparison with the crystal structure of the Fc wild-type protein reveals conservation of the overall domain structures but significant differences in EF-loop conformations. Furthermore, we present the first Fcab-antigen complex structures demonstrating the interaction between the engineered Fcab loops with domain IV of HER2. The crystal structures of the STAB19-HER2 and H10-03-6-HER2 complexes together with analyses by isothermal titration calorimetry, SEC-MALS, and fluorescence correlation spectroscopy show that one homodimeric Fcab binds two HER2 molecules following a negative cooperative binding behavior.

Fcab-HER2 Interaction: a Menage a Trois. Lessons from X-Ray and Solution Studies.,Lobner E, Humm AS, Goritzer K, Mlynek G, Puchinger MG, Hasenhindl C, Ruker F, Traxlmayr MW, Djinovic-Carugo K, Obinger C Structure. 2017 Jun 6;25(6):878-889.e5. doi: 10.1016/j.str.2017.04.014. Epub 2017, May 18. PMID:28528777^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.