Limits...
Structural basis of regiospecificity of a mononuclear iron enzyme in antibiotic fosfomycin biosynthesis.

Yun D, Dey M, Higgins LJ, Yan F, Liu HW, Drennan CL - J. Am. Chem. Soc. (2011)

Bottom Line: Hydroxypropylphosphonic acid epoxidase (HppE) is an unusual mononuclear iron enzyme that uses dioxygen to catalyze the oxidative epoxidation of (S)-2-hydroxypropylphosphonic acid (S-HPP) in the biosynthesis of the antibiotic fosfomycin.Additionally, the enzyme converts the R-enantiomer of the substrate (R-HPP) to 2-oxo-propylphosphonic acid.These structures, along with previously determined structures of S-HPP-HppE, identify the dioxygen binding site on iron and elegantly illustrate how HppE is able to recognize both substrate enantiomers to catalyze two completely distinct reactions.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.

ABSTRACT
Hydroxypropylphosphonic acid epoxidase (HppE) is an unusual mononuclear iron enzyme that uses dioxygen to catalyze the oxidative epoxidation of (S)-2-hydroxypropylphosphonic acid (S-HPP) in the biosynthesis of the antibiotic fosfomycin. Additionally, the enzyme converts the R-enantiomer of the substrate (R-HPP) to 2-oxo-propylphosphonic acid. To probe the mechanism of HppE regiospecificity, we determined three X-ray structures: R-HPP with inert cobalt-containing enzyme (Co(II)-HppE) at 2.1 Å resolution; R-HPP with active iron-containing enzyme (Fe(II)-HppE) at 3.0 Å resolution; and S-HPP-Fe(II)-HppE in complex with dioxygen mimic NO at 2.9 Å resolution. These structures, along with previously determined structures of S-HPP-HppE, identify the dioxygen binding site on iron and elegantly illustrate how HppE is able to recognize both substrate enantiomers to catalyze two completely distinct reactions.

Show MeSH

Related in: MedlinePlus

Structures of HppE with R-HPP or S-HPP bound in the active site. (a) Bidentate binding mode for R-HPP in the Co(II)–HppE structure. (b) Bidentate binding mode for R-HPP in Fe(II)–HppE structure. (c) Bidentate binding mode for S-HPP in the Co(II)–HppE structure (1ZZB monomer B). (d) Bidentate binding mode for S-HPP in the Fe(II)–HppE structure (1ZZ8 monomer C). Substrate and protein residues are shown as sticks (carbon (gray), oxygen (red), nitrogen (blue), phosphorus (purple)), water molecules as spheres (cyan), Co(II) as a sphere (magenta), and Fe(II) as a sphere (rust). The 2Fo – Fc maps (blue mesh) are contoured at 1.0 σ, and the Fo – Fc omit-maps (green mesh) of the substrate indicating the position of the phosphorus are contoured at 8.0, 10.0, 9.0, and 8.0 σ, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3140168&req=5

fig2: Structures of HppE with R-HPP or S-HPP bound in the active site. (a) Bidentate binding mode for R-HPP in the Co(II)–HppE structure. (b) Bidentate binding mode for R-HPP in Fe(II)–HppE structure. (c) Bidentate binding mode for S-HPP in the Co(II)–HppE structure (1ZZB monomer B). (d) Bidentate binding mode for S-HPP in the Fe(II)–HppE structure (1ZZ8 monomer C). Substrate and protein residues are shown as sticks (carbon (gray), oxygen (red), nitrogen (blue), phosphorus (purple)), water molecules as spheres (cyan), Co(II) as a sphere (magenta), and Fe(II) as a sphere (rust). The 2Fo – Fc maps (blue mesh) are contoured at 1.0 σ, and the Fo – Fc omit-maps (green mesh) of the substrate indicating the position of the phosphorus are contoured at 8.0, 10.0, 9.0, and 8.0 σ, respectively.

Mentions: The crystal structure of Co(II)–HppE in complex with R-HPP was solved to 2.1 Å resolution (Figure 2a, Supporting Information Table 1). R-HPP–Co(II)–HppE is catalytically inert under aerobic conditions(9) and allows us to observe at high resolution an enzyme state that mimics the form of the enzyme prior to dioxygen binding. We have also solved this same structure using the native Fe(II) metal ion in the absence of dioxygen (Figure 2b), but to lower resolution (3.0 Å). We find that the overall structures are similar, with root-mean-square deviations of 0.27–0.71 Å. In each case, substrate can be unambiguously positioned in the active site due to the presence of 8–10 σ electron density peaks that identify the position of the HPP phosphorus atom (Figure 2). As was the case for the S-enantiomer, R-HPP binds to the active site metal in a bidentate binding mode coordinated by both the C2 hydroxyl and the C1 phosphonate moieties (Figure 2a–d; also see Supporting Information Figure 1a–1e).(15) The bidentate binding mode is observed in both the Fe(II) and the Co(II) structures (see Supporting Information Table 2 for a complete list of structures).


Structural basis of regiospecificity of a mononuclear iron enzyme in antibiotic fosfomycin biosynthesis.

Yun D, Dey M, Higgins LJ, Yan F, Liu HW, Drennan CL - J. Am. Chem. Soc. (2011)

Structures of HppE with R-HPP or S-HPP bound in the active site. (a) Bidentate binding mode for R-HPP in the Co(II)–HppE structure. (b) Bidentate binding mode for R-HPP in Fe(II)–HppE structure. (c) Bidentate binding mode for S-HPP in the Co(II)–HppE structure (1ZZB monomer B). (d) Bidentate binding mode for S-HPP in the Fe(II)–HppE structure (1ZZ8 monomer C). Substrate and protein residues are shown as sticks (carbon (gray), oxygen (red), nitrogen (blue), phosphorus (purple)), water molecules as spheres (cyan), Co(II) as a sphere (magenta), and Fe(II) as a sphere (rust). The 2Fo – Fc maps (blue mesh) are contoured at 1.0 σ, and the Fo – Fc omit-maps (green mesh) of the substrate indicating the position of the phosphorus are contoured at 8.0, 10.0, 9.0, and 8.0 σ, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3140168&req=5

fig2: Structures of HppE with R-HPP or S-HPP bound in the active site. (a) Bidentate binding mode for R-HPP in the Co(II)–HppE structure. (b) Bidentate binding mode for R-HPP in Fe(II)–HppE structure. (c) Bidentate binding mode for S-HPP in the Co(II)–HppE structure (1ZZB monomer B). (d) Bidentate binding mode for S-HPP in the Fe(II)–HppE structure (1ZZ8 monomer C). Substrate and protein residues are shown as sticks (carbon (gray), oxygen (red), nitrogen (blue), phosphorus (purple)), water molecules as spheres (cyan), Co(II) as a sphere (magenta), and Fe(II) as a sphere (rust). The 2Fo – Fc maps (blue mesh) are contoured at 1.0 σ, and the Fo – Fc omit-maps (green mesh) of the substrate indicating the position of the phosphorus are contoured at 8.0, 10.0, 9.0, and 8.0 σ, respectively.
Mentions: The crystal structure of Co(II)–HppE in complex with R-HPP was solved to 2.1 Å resolution (Figure 2a, Supporting Information Table 1). R-HPP–Co(II)–HppE is catalytically inert under aerobic conditions(9) and allows us to observe at high resolution an enzyme state that mimics the form of the enzyme prior to dioxygen binding. We have also solved this same structure using the native Fe(II) metal ion in the absence of dioxygen (Figure 2b), but to lower resolution (3.0 Å). We find that the overall structures are similar, with root-mean-square deviations of 0.27–0.71 Å. In each case, substrate can be unambiguously positioned in the active site due to the presence of 8–10 σ electron density peaks that identify the position of the HPP phosphorus atom (Figure 2). As was the case for the S-enantiomer, R-HPP binds to the active site metal in a bidentate binding mode coordinated by both the C2 hydroxyl and the C1 phosphonate moieties (Figure 2a–d; also see Supporting Information Figure 1a–1e).(15) The bidentate binding mode is observed in both the Fe(II) and the Co(II) structures (see Supporting Information Table 2 for a complete list of structures).

Bottom Line: Hydroxypropylphosphonic acid epoxidase (HppE) is an unusual mononuclear iron enzyme that uses dioxygen to catalyze the oxidative epoxidation of (S)-2-hydroxypropylphosphonic acid (S-HPP) in the biosynthesis of the antibiotic fosfomycin.Additionally, the enzyme converts the R-enantiomer of the substrate (R-HPP) to 2-oxo-propylphosphonic acid.These structures, along with previously determined structures of S-HPP-HppE, identify the dioxygen binding site on iron and elegantly illustrate how HppE is able to recognize both substrate enantiomers to catalyze two completely distinct reactions.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.

ABSTRACT
Hydroxypropylphosphonic acid epoxidase (HppE) is an unusual mononuclear iron enzyme that uses dioxygen to catalyze the oxidative epoxidation of (S)-2-hydroxypropylphosphonic acid (S-HPP) in the biosynthesis of the antibiotic fosfomycin. Additionally, the enzyme converts the R-enantiomer of the substrate (R-HPP) to 2-oxo-propylphosphonic acid. To probe the mechanism of HppE regiospecificity, we determined three X-ray structures: R-HPP with inert cobalt-containing enzyme (Co(II)-HppE) at 2.1 Å resolution; R-HPP with active iron-containing enzyme (Fe(II)-HppE) at 3.0 Å resolution; and S-HPP-Fe(II)-HppE in complex with dioxygen mimic NO at 2.9 Å resolution. These structures, along with previously determined structures of S-HPP-HppE, identify the dioxygen binding site on iron and elegantly illustrate how HppE is able to recognize both substrate enantiomers to catalyze two completely distinct reactions.

Show MeSH
Related in: MedlinePlus