Crystal Structure of the Response Regulator 02 Receiver Domain, the Essential YycF Two-Component System of Streptococcus pneumoniae in both Complexed and Native States†

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   FIG. 1.

   Sequence alignment of RR02rec from S. pneumoniae and two other members of the YycF family from S. aureus and B. subtilis. The high degree of sequence similarity within this family can be seen, with over 60% of residues being identical. The linker region between the receiver domain and the effector domain shows little or no similarity. The secondary structure elements of RR02rec are shown above the alignment. The alternating pattern of helices and strands seen in all RR structures is shown. This figure was created using MultAlin (12) and ESPript (22).
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   FIG. 2.

   Ribbon diagram of the dimer seen in the crystal structure. Figures were created using MOLSCRIPT (32), BOBSCRIPT (17), and Raster3D (39).
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   FIG. 3.

   Close-up stereo views of the active site of RR02rec showing several conserved residues of the RR family. (a) Position of the P_i ion outside the active site. (b) Acetate coordinated in the active site mimicking the role of a P_i ion. (c) Native RR02rec structure. Final 2FoFc maps contoured at 2 sigma. Figures were created using MOLSCRIPT (32), BOBSCRIPT (17), and Raster3D (39).
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   FIG. 4.

   (a) Overlay of two of the structures presented in this paper (acetate in yellow and P_i in green). (b) Stereo view showing the β3-α3 loop and residues 56 to 63. The orange ribbon represents the structure of acetate-coordinated RR02rec, and the purple ribbon represents the phosphate coordinated outside the active site. Figures were created using MOLSCRIPT (32), BOBSCRIPT (17), and Raster3D (39).
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   FIG. 5.

   Stereo diagrams of the Cα traces of RR02rec. The native form (shown in red) and PhoB (in green) (PDB code 1B00) (48), DrrD (in blue) (PDB code 1KGS) (10), DrrB (in purple) (PDB code 1P2F) (46), and PhoP (in yellow) (PDB code 1MVO) (7) are shown. Superimposition and RMSDs were performed using the CCP4i program LSQKAB (30). Figures were created using MOLSCRIPT (32), BOBSCRIPT (17), and Raster3D (39).

• American Society for Microbiology