2016 年 58 巻 2 号 p. 91-95
Many molluscs use hemocyanin freely dissolved in hemolymph for oxygen transportation. Hemocyanin is one of the largest known proteins, of which total molecular mass is larger than 3.3 MDa. Although molluscan hemocyanin is used as immunotherapeutic agents, their detailed structures had not yet been revealed. As its enormous size and the propensity of dissociation hampered crystallization, structural studies have relied mainly on electron microscopy. To understand the oxygen transportation mechanism in detail and promote the biomedical application, high-resolution structure has been desired for a long time. In this study, we successfully determined the X-ray crystal structure of the intact 3.8-MDa hemocyanin from Japanese flying squid at 3.0 Å resolution, which revealed the detailed molecular architecture of the supermolecule.