Journal Article ビリン還元酵素PcyAと基質ビリベルジン複合体の中性子結晶構造解析で見えてきたもの

玉田, 太郎  ,  海野, 昌喜(茨城大学大学院理工学研究科)  ,  日下, 勝弘(茨城大学フロンティア応用原子科学研究センター)  ,  杉島, 正一(久留米大学医学部)  ,  和田, 啓(宮崎大学テニュアトラック推進機構)  ,  萩原, 義徳(久留米工業高等専門学校生物応用化学科)  ,  福山, 恵一(大阪大学大学院工学研究科)

26 ( 3 )  , pp.130 - 134 , 2016-08 , 日本中性子科学会
Phycocyanobilin:ferredoxin oxidoreductase (PcyA) catalyzes the conversion of biliverdin (BV) to phycocyanobilin, a light harvesting pigment. To visualize the hydrogens (and protons) in this unique enzyme, we conducted neutron crystallography of the PcyA-BV complex. In the enzyme, BV bound to PcyA was in equilibrium between the neutral (BV) and the protonated (BVH+) forms. Both of the structures including the hydrogen atoms could be determined. The protonation of the nearby essential residue Asp105 was complemented with the BV protonation states. His88, an essential residue, was protonated to form a hydrogen bond to a lactam oxygen of the BV A-ring. His88 is also hydrogen-bonded to His74 via a hydronium ion. In this article, we also describe the story to grow the large crystals of the PcyA-BV complex and its neutron diffraction experiment.

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