PDBsum entry 1ft9

Transcription

PDB id: 1ft9

Contents

Protein chains

210 a.a. *

Ligands

HEM ×2

Waters ×199

* Residue conservation analysis

PDB id:

1ft9

Name:

Transcription

Title:

Structure of the reduced (feii) co-sensing protein from r. Rubrum

Structure:

Carbon monoxide oxidation system transcription regulator. Chain: a, b. Synonym: cooa gene product. Engineered: yes

Source:

Rhodospirillum rubrum. Organism_taxid: 1085. Expressed in: escherichia coli. Expression_system_taxid: 562

Biol. unit:

Dimer (from PQS)

Resolution:

2.60Å R-factor: 0.230 R-free: 0.280

Authors:

W.N.Lanzilotta,D.J.Schuller,T.L.Poulos,M.V.Thorsteinsson,B.Kirby, G.P.Roberts

Key ref:

W.N.Lanzilotta et al. (2000). Structure of the CO sensing transcription activator CooA. Nat Struct Biol, 7, 876-880. PubMed id: 11017196 DOI: 10.1038/82820

Date:

12-Sep-00 Release date: 09-Oct-00

Protein chains

P72322  (P72322_RHORU) -  CooA protein from Rhodospirillum rubrum

Seq: 222 a.a.

Struc: 210 a.a.

DOI no: 10.1038/82820

Nat Struct Biol 7:876-880 (2000)

PubMed id: 11017196

Structure of the CO sensing transcription activator CooA.

W.N.Lanzilotta, D.J.Schuller, M.V.Thorsteinsson, R.L.Kerby, G.P.Roberts, T.L.Poulos.

ABSTRACT

CooA is a homodimeric transcription factor that belongs to the catabolite activator protein (CAP) family. Binding of CO to the heme groups of CooA leads to the transcription of genes involved in CO oxidation in Rhodospirillum rubrum. The 2.6 A structure of reduced (Fe2+) CooA reveals that His 77 in both subunits provides one heme ligand while the N-terminal nitrogen of Pro 2 from the opposite subunit provides the other ligand. A structural comparison of CooA in the absence of effector and DNA (off state) with that of CAP in the effector and DNA bound state (on state) leads to a plausible model for the mechanism of allosteric control in this class of proteins as well as the CO dependent activation of CooA.

Selected figure(s)

Figure 1.
Figure 1. Comparison of the overall fold and conformational differences between CooA and CAP with cAMP and DNA bound. a, Stereo view of CooA and CAP dimers. In both cases, the effector binding domain (residues 2−107 for Cooa, 9−111 for CAP), C helix (residues 108−130 for CooA, 112−135 for CAP), and DNA binding domain (residues 131−213 for CooA, 136−205 for CAP) of monomer A are colored dark blue, dark pink, and purple, respectively. For monomer B, the effector binding domain, C helix, and the DNA binding domain are colored dark green, light green, and cyan, respectively. Both the heme groups of CooA and the cAMP molecules of CAP are represented by red space-filling models. The structure of CAP was adapted from Shultz et al.^4. b, Superposition of the effector domains of monomer B for CooA (shown in blue) and CAP (shown in orange) showing the relative orientations of the C helices. The r.m.s.d. for the alignment of the backbone atoms in the core structural elements of the effector domain was 1.16 Å. Strictly conserved Pro and Leu residues are shown at the N-terminal and C-terminal ends of the C helices, respectively. While an individual effector domain of CooA (green) aligns well with one of CAP (orange), the orientation of the C helix in the second domain is completely different. Of particular interest is the movement of the C helix (yellow arrow) when the structure of CooA (no effector bound) is compared with that of CAP (effector bound). c, View looking down the C helices from the N-terminus toward the C-terminus. The alignment is the same as shown in (b), with the yellow arrow representing movement from the effector free (CooA) to the effector bound (CAP) state. d, Alignment of effector domains in monomer B for CooA and CAP with the DNA binding domains shown. As can be seen, the relative position of the DNA binding domain and subsequently the position of the recognition helix in CooA is rotated 180° away from the position observed in the structure of CAP with effector bound.

Figure 3.
Figure 3. Stereo views of the heme environment in CooA. a, Back view and b, side view of the F[o] - F[c] omit map (green cage), contoured at 3 by the simulated annealing protocol with Pro 2, Pro 3 and the heme omitted. c, Anomalous difference maps for data collected at 1.91 Å are shown contoured at 14 (purple cage) and 3 (green cage) for the heme iron and sulfur atom of Cys 75, respectively. The peak on the sulfur provides unambiguous confirmation on the correct orientation of the Cys 75 side chain. In going to the on state, one axial heme ligand must be displaced in order to allow CO to coordinate the heme iron. The N-Fe distance is 2.1 Å for both the His and Pro ligands with continuous electron density to the iron, so one bond cannot be judged to be more labile than the other based on the structure alone. Our model of the allosteric switch places the C helix of molecule B very close to the Pro in molecule A that coordinates heme B, suggesting that the allosteric switch involves displacement of the Pro ligand. However, if the entire heme were to move then it is possible that the Pro remains coordinated and that the His ligand is displaced. Our model cannot distinguish between these two possibilities.

The above figures are reprinted by permission from Macmillan Publishers Ltd: Nat Struct Biol (2000, 7, 876-880) copyright 2000.

Figures were selected by an automated process.