[1P-1] Poster 1 (1P-01ー1P-48)

[1P-27] Structural and functional analysis of tomato HY2 which synthesizes the chromophore for plant phytochrome

^○Masakazu Sugishima¹, Kei Wada², Natsuki Saito³, Masaki Unno⁴, Keiichi Fukuyama⁵, Ken Yamamoto¹ (1.Dept. of Med. Biochem., Kurume Univ. Sch. of Med., 2.Dept. of Med. Sci., Univ. of Miyazaki, 3.Col. of Eng., Ibaraki Univ., 4.Grad. Sch. of Sci. and Eng., Ibaraki Univ., 5.Dept. of Biol. Sci., Grad. Sch. of Sci., Osaka Univ.)

Ferredoxin-dependent bilin reductases (FDBR) catalyzes the site-specific reduction of a heme-metabolite, biliverdin (BV), to produce phytobilins. Phytobilins are utilized as photosynthetic and light sensitive pigments in cyanobactearia, red algae, and plants [1]. Phytochromobilin (PφB), one of phytobilins, is utilized as a sensory pigment in phytochrome, a major red-light photoreceptor in plants. PφB is produced by PφB synthetase, HY2, which catalyzes the site-specific reduction of the BV A-ring. Following this enzymatic reaction, the A-ring of PφB can be covalently attached to apo-phytochrome.
Here we determined the crystal structure of tomato HY2 in complex with BV at 1.95 angstrom resolution. Although the overall structures of previously determined FDBR and that of HY2 are similar with each other, BV in HY2 is inverted relative to that in other FDBR, and the configuration of BV in HY2 is ZZZssa whereas that in other FDBR is ZZZsss. Site-directed mutagenesis of HY2 based on the crystal structure suggests the mechanisms of site-specific reduction and product release [2].

References
[1] Sugishima M et al. Curr. Opin. Struct. Biol. (2019) 59, 73-80
[2] Sugishima M et al. J. Biol. Chem. (2020) 295, 771-782