title: Bacteriophytochromes are photochromic histidine kinases using a biliverdin chromophore.
abstract: Phytochromes comprise a principal family of red/far-red light sensors in plants. Although phytochromes were thought originally to be confined to photosynthetic organisms, we have recently detected phytochrome-like proteins in two heterotrophic eubacteria, Deinococcus radiodurans and Pseudomonas aeruginosa. Here we show that these form part of a widespread family of bacteriophytochromes (BphPs) with homology to two-component sensor histidine kinases. Whereas plant phytochromes use phytochromobilin as the chromophore, BphPs assemble with biliverdin, an immediate breakdown product of haem, to generate photochromic kinases that are modulated by red and far-red light. In some cases, a unique haem oxygenase responsible for the synthesis of biliverdin is part of the BphP operon. Co-expression of this oxygenase with a BphP apoprotein and a haem source is sufficient to assemble holo-BphP in vivo. Both their presence in many diverse bacteria and their simplified assembly with biliverdin suggest that BphPs are the progenitors of phytochrome-type photoreceptors.
authors.affiliation: Cellular and Molecular Biology Program, Department of Horticulture, University of Wisconsin-Madison, 1575 Linden Drive, Madison, Wisconsin 53706, USA.
authors.forename: S H
authors.initials: SH
authors.lastname: Bhoo
authors.forename: S J
authors.initials: SJ
authors.lastname: Davis
authors.forename: J
authors.initials: J
authors.lastname: Walker
authors.forename: B
authors.initials: B
authors.lastname: Karniol
authors.forename: R D
authors.initials: RD
authors.lastname: Vierstra
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D001664:Biliverdine / Q000737:chemistry / Q000378:metabolism*; D003001:Cloning, Molecular; D004926:Escherichia coli; D019143:Evolution, Molecular; D006095:Gram-Positive Cocci / Q000737:chemistry / Q000378:metabolism*; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics / Q000378:metabolism; D006639:Histidine / Q000378:metabolism; D000071677:Histidine Kinase; D008027:Light; D008969:Molecular Sequence Data; D009876:Operon; D010766:Phosphorylation; D010777:Photochemistry; D020283:Photoreceptors, Microbial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D011485:Protein Binding; D011494:Protein Kinases / Q000737:chemistry / Q000378:metabolism* / Q000528:radiation effects; D011550:Pseudomonas aeruginosa / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D020283:Photoreceptors, Microbial; D011994:Recombinant Proteins; D006639:Histidine; D006419:Heme Oxygenase (Decyclizing); D011494:Protein Kinases; D000071677:Histidine Kinase; D001664:Biliverdine