Disease relevance of HY2

• To test the catalytic activities of these putative enzymes, representative HY2-related genes from each class were amplified by the polymerase chain reaction and expressed in Escherichia coli [1].
• 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].

High impact information on HY2

• We have identified at least three Arabidopsis nuclear genes (GUN1, GUN2, and GUN3) necessary for coupling the expression of some nuclear genes to the functional state of the chloroplast [2].
• Database searches and hybridization studies suggest that HY2 is a unique gene in the Arabidopsis genome that is related to a family of proteins found in oxygenic photosynthetic bacteria [3].
• The HY2 transit peptide is sufficient to localize the reporter green fluorescent protein to plastids [3].
• Purified mature recombinant HY2 protein exhibits P Phi B synthase activity (i.e., ferredoxin-dependent reduction of biliverdin IX alpha to P Phi B), as confirmed by HPLC and by the ability of the bilin reaction products to combine with apophytochrome to yield photoactive holophytochrome [3].
• By expressed sequence tag (EST)-based screening of sequence databases, we found a tomato gene that encodes a protein homologous to Arabidopsis HY2 for phytochromobilin synthase catalyzing the last step of phytochrome chromophore biosynthesis [4].

Associations of HY2 with chemical compounds

• 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].

References