title: Crystal structure of a cyanobacterial phytochrome response regulator.
abstract: The two-component signal transduction pathway widespread in prokaryotes, fungi, molds, and some plants involves an elaborate phosphorelay cascade. Rcp1 is the phosphate receiver module in a two-component system controlling the light response of cyanobacteria Synechocystis sp. via cyanobacterial phytochrome Cph1, which recognizes Rcp1 and transfers its phosphoryl group to an aspartate residue in response to light. Here we describe the crystal structure of Rcp1 refined to a crystallographic R-factor of 18.8% at a resolution of 1.9 A. The structure reveals a tightly associated homodimer with monomers comprised of doubly wound five-stranded parallel beta-sheets forming a single-domain protein homologous with the N-terminal activator domain of other response regulators (e.g., chemotaxis protein CheY). The three-dimensional structure of Rcp1 appears consistent with the conserved activation mechanism of phosphate receiver proteins, although in this case, the C-terminal half of its regulatory domain, which undergoes structural changes upon phosphorylation, contributes to the dimerization interface. The involvement of the residues undergoing phosphorylation-induced conformational changes at the dimeric interface suggests that dimerization of Rcp1 may be regulated by phosphorylation, which could affect the interaction of Rcp1 with downstream target molecules.
authors.affiliation: Department of Life Science, Kwangju Institute of Science and Technology, Kwangju 500-712, Korea.
authors.forename: Young Jun
authors.initials: YJ
authors.lastname: Im
authors.forename: Seong-Hwan
authors.initials: SH
authors.lastname: Rho
authors.forename: Chung-Mo
authors.initials: CM
authors.lastname: Park
authors.forename: Song-Sook
authors.initials: SS
authors.lastname: Yang
authors.forename: Jeong-Gu
authors.initials: JG
authors.lastname: Kang
authors.forename: Jae Young
authors.initials: JY
authors.lastname: Lee
authors.forename: Pill-Soon
authors.initials: PS
authors.lastname: Song
authors.forename: Soo Hyun
authors.initials: SH
authors.lastname: Eom
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry; D001665:Binding Sites; D000458:Cyanobacteria / Q000737:chemistry* / Q000502:physiology; D019281:Dimerization; D008345:Manganese / Q000737:chemistry / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry; D000072236:Methyl-Accepting Chemotaxis Proteins; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010766:Phosphorylation; D020283:Photoreceptors, Microbial; D010834:Phytochrome / Q000737:chemistry / Q000502:physiology; D011487:Protein Conformation; D011494:Protein Kinases / Q000737:chemistry / Q000502:physiology; D011506:Proteins / Q000737:chemistry*; D015398:Signal Transduction
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; D020283:Photoreceptors, Microbial; D011506:Proteins; C107945:Rcp1 protein, Synechocystis; D010834:Phytochrome; D008345:Manganese; D011494:Protein Kinases; C413623:Cph1 phytochrome protein, bacteria