Bilin-dependent regulation of chlorophyll biosynthesis by GUN4

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 118; no. 20
• Main Authors: Zhang, Weiqing, Willows, Robert D., Deng, Rui, Li, Zheng, Li, Mengqi, Wang, Yan, Guo, Yunling, Shi, Weida, Fan, Qiuling, Martin, Shelley S., Rockwell, Nathan C., Lagarias, J. Clark, Duanmu, Deqiang
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 11.05.2021
• Subjects: Science & Technology - Other Topics
• ISSN: 0027-8424; 1091-6490

Significance Enzymes of the chlorophyll biosynthetic pathway, which bind protoporphyrin and Mg-porphyrins, are susceptible to damage by singlet oxygen production in the presence of light and oxygen. These studies show that heme-derived linear tetrapyrroles (bilins) both stimulate and protect the protoporphyrin-binding CHLH subunit of Mg chelatase, the first committed enzyme of the chlorophyll synthesis, from self-sensitized photodamage and turnover via formation of nonphotosensitizing GENOMES UNCOUPLED 4 (GUN4):bilin:porphyrin adducts, which deliver protoporphyrin to CHLH. GUN4:bilin adducts likely evolved to sustain chlorophyll biosynthesis in an oxic world, accounting for retention of bilin synthesis in nearly all oxygenic photosynthetic species on Earth.