Saori Ichikawa, Toshiro Takai, Takashi Inoue, Toshifumi Yuuki, Yasushi Okumura, Kenji Ogura, Fuyuhiko Inagaki, Hideki Hatanaka; NMR Study on the Major Mite Allergen Der f 2: Its Refined Tertiary Structure, Epitopes for Monoclonal Antibodies and Characteristics Shared by ML Protein Group Members. J Biochem 2005; 137 (3): 255-263. doi: 10.1093/jb/mvi039
Group 2 major mite allergens Der f 2 and Der p 2 are classified into the recently identified group of MD-2-related lipid-recognition (ML) proteins, but the ligands and biological functions of these allergens are unknown. We have obtained a high-quality NMR structure for Der f 2, and found that it is more similar to the crystal structure of NPC2, a distant homologue, than to that of Der p 2, in terms of the separation and angle between the two major β-sheets. This made us propose that ML proteins undergo clamshell-like motions that change the sizes of ligand-binding spaces inside their immunoglobulin-fold β-sandwich to accommodate lipid molecules. This type of motion in lipopolysaccaride recognition of MD-2 is suggested to be likely as well by structural models. We also report the applicability of NMR differential exchange broadening experiments for complexes of intact monoclonal antibodies and antigens; using this technique, we have detected the conformational epitopes for monoclonal antibodies 15E11 and 13A4 as two separate surface patches.