Ku, Li-Wen , Chen, Hsiu-Chen , Tu, Shih-Long .
Spectroscopic and mutagenesis studies of phytochromobilin synthase HY2 from Arabidopsis.
Phytobilins are linear tetrapyrrole molecules that function as the prosthetic groups of light sensing phytochromes in plants and light harvesting phycobilisomes in cyanobacteria and algae. Derived from heme, phytobilins are synthesized through a linear tetrapyrrole intermediate, biliverdin IXalpha, in the phytobilin biosynthesis pathwayï€® Biliverdin IXalpha is reduced into different phytobilins in plants, cyanobacteria and algae by different ferredoxin-dependent bilin reductases with distinct double-bond specificities. In Arabidopsis, HY2 (LONG HYPOCOTYL 2) gene encodes a phytochromobilin synthase catalyzes the ferredoxin-dependent reaction of double bond reduction at the A-ring endo-vinyl group of biliverdin IXalpha to yield phytochromobilin. Mutations in HY2 have been shown to severely affect light-regulated physiological processes due to the loss of all functional phytochromes. In this study, we seek to determine the structure and function of HY2. Approaches including structural homology modeling, spectroscopic analysis and site-directed mutagenesis showed several potential proton donating residues in the active site are involved in the catalytic steps. A mechanistic prediction of HY2 reaction was proposed.
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1 - Institute of Plant and Microbial Biology, Academia Sinica
2 - Institute of Plant and Microbial Biology, Academia Sinica, 128 Sec. 2, Academia Road, Nankang, Taipei, 11529, Taiwan
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM