Professor, Nagaoka University of Technology.

Born in Tokyo, Japan, Prof. Mitsui graduated from the Department of Pharmaceutical Science of the University of Tokyo and obtained his Ph.D. in 1966. After graduation, he moved to Yale University, New Haven, Connecticut, to learn protein crystallography under Professors H.W. Wyckoff and F.M. Richards. In 1971, he started research on protein crystallography at the University of Tokyo. He was one of the pioneers of protein crystallography in Japan, and led the Crystallographic Society of Japan for many years.

He revealed several three-dimension al structures of crystallized proteins in his lifetime, including those of Streptomyces subtilisin inhibitor, its complex with subtilisin, ribonucleases, murine interferon beta, and extradiol-type dioxygenases. Among such structures, determination of the crystal structure of murine interferon beta was one of his outstanding achievements. It took great effort and longer than seven years to determine its structure. Prof. Mitsui also was interested in the evolutionary aspects of IFN and cytokines. Based on comparison of the sequences of various cytokines and their cognate receptors, he proposed the coupled evolution of the ligand-receptor system of cytokines.

Prof. Mitsui was known by his students, staff, collaborators and colleagues as a warm and kindhearted person.  He talked with students not only about the science but also on a broad range of subjects from social issues to entertainment. His friendly attitude made the laboratory in Nagaoka attractive, and many students who had graduated from his laboratory would visit him every summer when the firework festival, a very famous event in Japan, was held in Nagaoka. Of course, his interferon research, which started in Tokyo and blossomed in Nagaoka, also attracted many students to Prof. Mitsui’s laboratory.

Yukio Mitsui, a most distinguished scholar in protein crystallography, passed away on January 19, 2000, at the age of 61. His wife, Mrs. Etsuko Mitsui, said that he was always very happy when meeting with friends and colleagues who worked in the field of interferon research and that his receipt of The Milstein Award in Budapest in 1994 was the most memorable event of his lifetime. On his death, Japanese newspapers of January 20, 2000, reported: A great winner of The Milstein Award for interferon and cytokine research, Prof. Yukio Mitsui, has passed away. He dedicated his life to elucidating the structure of interferons. An obituary of Yukio Mitsui has been published in the Journal of Interferon and Cytokine Research.

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