Disease relevance of Phytochromobilin

• By exploiting the sequence of phytochromobilin synthase (HY2) of Arabidopsis, an enzyme that catalyzes the ferredoxin-dependent conversion of BV to the phytochrome chromophore precursor phytochromobilin, genes encoding putative bilin reductases were identified in the genomes of various cyanobacteria, oxyphotobacteria, and plants [1].
• The Cph2 was overexpressed in E. coli as an Intein/CBD (chitin binding domain) fusion and in vitro reconstituted with phycocyanobilin (PCB) or phytochromobilin (PPhiB) [2].

High impact information on Phytochromobilin

• Light perception by the plant photoreceptor phytochrome requires the tetrapyrrole chromophore phytochromobilin (P Phi B), which is covalently attached to a large apoprotein [3].
• Because the mammalian enzyme biliverdin IX alpha reductase (BVR) is able to functionally inactivate phytochromobilin in vitro, this investigation was undertaken to determine whether BVR expression in transgenic plants would prevent the synthesis of functionally active phytochrome in vivo [4].
• We also show that gun2 and gun3 are alleles of the known photomorphogenic mutants, hy1 and hy2, which are required for phytochromobilin synthesis from heme [5].
• HPLC analyses confirm that biliverdin is converted to both 3E- and 3Z-isomers of phytochromobilin [6].
• Assembly of holophytochrome in the plant cell requires covalent attachment of the linear tetrapyrrole chromophore precursor, phytochromobilin, to a unique cysteine in the nascent apoprotein [7].

Chemical compound and disease context of Phytochromobilin

• Metabolic engineering to produce phytochromes with phytochromobilin, phycocyanobilin, or phycoerythrobilin chromophore in Escherichia coli [8].

Anatomical context of Phytochromobilin

• These results, together with experiments using boiled plastids, indicate that phytochromobilin synthesis from biliverdin is enzyme-mediated [9].

Associations of Phytochromobilin with other chemical compounds

• Phytochrome, a red/far-red light receptor, has phytochromobilin as its chromophore, whereas the blue/near UV photoreceptors cryptochrome and phototropin have a pair of flavin derivatives [10].
• Experiments where NADPH (and ATP) levels in intact developing chloroplasts are manipulated by feeding the metabolites 3-phosphoglycerate, dihydroxyacetone phosphate, and glucose 6-phosphate or by illumination with white light, support the hypothesis that the enzyme that accomplishes this conversion, phytochromobilin synthase, is plastid-localized [9].
• The recombinant 65-kDa polypeptide of phyA oat phytochrome was expressed by yeast Pichia pastoris and assembled into two chromopeptides with the chromophores phytochromobilin (PphiB) and phycocyanobilin (PCB), respectively [11].
• We present an overview of excited state quantum chemical calculations aimed at elucidating controversial issues regarding the photochemistry of the protein-bound chromophores astaxanthin and phytochromobilin [12].

Gene context of Phytochromobilin

• Normal mode calculations correlate this frequency drop with a change in the geometry of the C15 methine bridge of the phytochromobilin chromophore [13].

References