title: Signaling kinetics of cyanobacterial phytochrome Cph1, a light regulated histidine kinase.
abstract: Cyanobacterial phytochrome 1 (Cph1) is a red/far-red light regulated histidine kinase, which together with its response regulator (Rcp1) forms a two-component light signaling system in Synechocystis 6803. In the present study we followed the in vitro autophosphorylation of Cph1 and the subsequent phosphotransfer to Rcp1 in different ionic milieus and following different light treatments. Both processes were red/far-red reversible with activity manifested in the Pr ground state (in darkness or after far-red irradiation) and with strongest activities being exhibited in the presence of Mn(2+). In vivo and in vitro assembled holoproteins in the Pr state displayed at least 4-fold higher efficiencies (k(cat)/K(m)) for autophosphorylation and phosphotransfer than the apoprotein or the holoprotein at photoequilibrium in red light. The reduced activities observed following red light treatments were consistent with the Pfr state being enzymatically inactive. Thus, both the rate of kinase autophosphorylation and the rate of phosphotransfer regulate the phosphorylation state of the response regulator, consistent with the rotary switch model regulating accessibility of the histidine target.
authors.affiliation: Institute for Plant Physiology, Justus Liebig University, Senckenbergstrasse 3, D35390 Giessen, Germany.
authors.forename: Georgios
authors.initials: G
authors.lastname: Psakis
authors.forename: Jo
authors.initials: J
authors.lastname: Mailliet
authors.forename: Christina
authors.initials: C
authors.lastname: Lang
authors.forename: Lotte
authors.initials: L
authors.lastname: Teufel
authors.forename: Lars-Oliver
authors.initials: LO
authors.lastname: Essen
authors.forename: Jon
authors.initials: J
authors.lastname: Hughes
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology* / Q000528:radiation effects; D002413:Cations, Divalent / Q000737:chemistry; D000071677:Histidine Kinase; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008027:Light; D008345:Manganese / Q000737:chemistry; D010750:Phosphoproteins / Q000737:chemistry / Q000502:physiology / Q000528:radiation effects; D010766:Phosphorylation / Q000528:radiation effects; D020283:Photoreceptors, Microbial; D010834:Phytochrome / Q000737:chemistry* / Q000502:physiology* / Q000528:radiation effects; D011494:Protein Kinases / Q000737:chemistry* / Q000378:metabolism* / Q000502:physiology* / Q000528:radiation effects; D015398:Signal Transduction / Q000502:physiology* / Q000528:radiation effects; D046939:Synechocystis / Q000201:enzymology* / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D001426:Bacterial Proteins; D002413:Cations, Divalent; D010750:Phosphoproteins; D020283:Photoreceptors, Microbial; C107945:Rcp1 protein, Synechocystis; D010834:Phytochrome; D008345:Manganese; D011494:Protein Kinases; D000071677:Histidine Kinase; C413623:Cph1 phytochrome protein, bacteria