PDBsum entry 1i3c

Signaling protein

PDB id: 1i3c

Contents

Protein chains

144 a.a. *

Ligands

SO4 ×5

Waters ×269

* Residue conservation analysis

References listed in PDB file

Key reference

Title

Crystal structure of a cyanobacterial phytochrome response regulator.

Authors

Y.J.Im, S.H.Rho, C.M.Park, S.S.Yang, J.G.Kang, J.Y.Lee, P.S.Song, S.H.Eom.

Ref.

Protein Sci, 2002, 11, 614-624. [DOI no: 10.1110/ps.39102]

PubMed id

11847283

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.

Figure 2.
Fig. 2. (a) Superposition of Rcp1 (blue) and CheY (yellow, PDB id 3chy; Volz and Matsumura 1991). The structurally well-conserved five-stranded ß core was used for structure superposition. (b) Superposition of the backbone structures of ß5 and 5 of Rcp1 (blue) and CheY (orange). The side chains of Ser121 in Rcp1 and Pro110 in CheY are shown for clarity. (c) Stereoview of the Rcp1 dimer. Molecule A is shown in blue and molecule B in red. The three secondary structures participating in the dimer interface are indicated.

Figure 3.
Fig. 3. Stereoview of the Rcp1 active site. (a) Active site in molecule A of the apo-Rcp1 structure. All interactions depicted by dashed lines are between 2.5 and 3.5 Å. (b) Active site in molecule A of the Mn-Rcp1 structure. Mn2+ is shown as a green sphere.

The above figures are reprinted by permission from the Protein Society: Protein Sci (2002, 11, 614-624) copyright 2002.