title: Eukaryotic phytochromes: light-regulated serine/threonine protein kinases with histidine kinase ancestry.
abstract: The discovery of cyanobacterial phytochrome histidine kinases, together with the evidence that phytochromes from higher plants display protein kinase activity, bind ATP analogs, and possess C-terminal domains similar to bacterial histidine kinases, has fueled the controversial hypothesis that the eukaryotic phytochrome family of photoreceptors are light-regulated enzymes. Here we demonstrate that purified recombinant phytochromes from a higher plant and a green alga exhibit serine/threonine kinase activity similar to that of phytochrome isolated from dark grown seedlings. Phosphorylation of recombinant oat phytochrome is a light- and chromophore-regulated intramolecular process. Based on comparative protein sequence alignments and biochemical cross-talk experiments with the response regulator substrate of the cyanobacterial phytochrome Cph1, we propose that eukaryotic phytochromes are histidine kinase paralogs with serine/threonine specificity whose enzymatic activity diverged from that of a prokaryotic ancestor after duplication of the transmitter module.
authors.affiliation: Section of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA.
authors.forename: K C
authors.initials: KC
authors.lastname: Yeh
authors.forename: J C
authors.initials: JC
authors.lastname: Lagarias
mesh_terms: D000595:Amino Acid Sequence; D000071677:Histidine Kinase; D008027:Light; D008969:Molecular Sequence Data; D010786:Photoreceptor Cells / Q000201:enzymology*; D018521:Plant Physiological Phenomena; D011494:Protein Kinases / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D011994:Recombinant Proteins; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D000071677:Histidine Kinase