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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.

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Comparison of the cantilever hairpins (β-strands labeled 1 and 2) of the R-HPP–Fe(II)–HppE structure (green) and the S-HPP–Fe(II)–HppE structure (cyan). Bound substrate and selected residues are shown as sticks, and iron atoms are shown as spheres (rust).
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fig3: Comparison of the cantilever hairpins (β-strands labeled 1 and 2) of the R-HPP–Fe(II)–HppE structure (green) and the S-HPP–Fe(II)–HppE structure (cyan). Bound substrate and selected residues are shown as sticks, and iron atoms are shown as spheres (rust).

Mentions: HppE appears to use an induced-fit mechanism to protect high-energy iron–oxygen species formed during catalysis.(15) A β-hairpin called the cantilever hairpin (residues 90–107) responds to the physiological substrate S-HPP when bound to the enzyme in the correct orientation by moving in and sealing off the top portion of the active site, leaving only a small opening for dioxygen to enter.(15) Comparison of S-HPP–Fe(II)–HppE structures with the alternative R-HPP substrate shows a similar response; the cantilever hairpin closes down and becomes more ordered upon bidentate substrate binding. In fact, in the closed conformation, the cantilever hairpin in the R-HPP–Fe(II)–HppE structure superimposes well with that in the S-HPP–Fe(II)–HppE structure (PDB ID 1ZZ8) (Figure 3), producing very similar interactions between the protein and S- and R-HPP substrates.


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)

Comparison of the cantilever hairpins (β-strands labeled 1 and 2) of the R-HPP–Fe(II)–HppE structure (green) and the S-HPP–Fe(II)–HppE structure (cyan). Bound substrate and selected residues are shown as sticks, and iron atoms are shown as spheres (rust).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig3: Comparison of the cantilever hairpins (β-strands labeled 1 and 2) of the R-HPP–Fe(II)–HppE structure (green) and the S-HPP–Fe(II)–HppE structure (cyan). Bound substrate and selected residues are shown as sticks, and iron atoms are shown as spheres (rust).
Mentions: HppE appears to use an induced-fit mechanism to protect high-energy iron–oxygen species formed during catalysis.(15) A β-hairpin called the cantilever hairpin (residues 90–107) responds to the physiological substrate S-HPP when bound to the enzyme in the correct orientation by moving in and sealing off the top portion of the active site, leaving only a small opening for dioxygen to enter.(15) Comparison of S-HPP–Fe(II)–HppE structures with the alternative R-HPP substrate shows a similar response; the cantilever hairpin closes down and becomes more ordered upon bidentate substrate binding. In fact, in the closed conformation, the cantilever hairpin in the R-HPP–Fe(II)–HppE structure superimposes well with that in the S-HPP–Fe(II)–HppE structure (PDB ID 1ZZ8) (Figure 3), producing very similar interactions between the protein and S- and R-HPP substrates.

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