PDBsum entry 2bnm

Oxidoreductase

PDB id: 2bnm

Contents

Protein chains

194 a.a. *

Ligands

SO4 ×15

Metals

_ZN ×2

Waters ×547

* Residue conservation analysis

PDB id:

2bnm

Name:

Oxidoreductase

Title:

The structure of hydroxypropylphosphonic acid epoxidase from s. Wedmorenis.

Structure:

Epoxidase. Chain: a, b. Synonym: hydroxypropylphosphonic acid epoxidase. Engineered: yes

Source:

Streptomyces wedmorensis. Organism_taxid: 43759. Expressed in: escherichia coli. Expression_system_taxid: 469008.

Biol. unit:

Tetramer (from PDB file)

Resolution:

1.70Å R-factor: 0.191 R-free: 0.230

Authors:

K.Mcluskey,S.Cameron,W.N.Hunter

Key ref:

K.McLuskey et al. (2005). Structure and reactivity of hydroxypropylphosphonic acid epoxidase in fosfomycin biosynthesis by a cation- and flavin-dependent mechanism. Proc Natl Acad Sci U S A, 102, 14221-14226. PubMed id: 16186494 DOI: 10.1073/pnas.0504314102

Date:

29-Mar-05 Release date: 05-Oct-05

Protein chains

Q56185  (HPPE_STRWE) -  (S)-2-hydroxypropylphosphonic acid epoxidase from Streptomyces wedmorensis

Seq: 198 a.a.

Struc: 194 a.a.

Enzyme reactions

• Enzyme class: E.C.1.11.1.23 - (S)-2-hydroxypropylphosphonic acid epoxidase.
• Reaction: (S)-2-hydroxypropylphosphonate + H2O2 = (1R,2S)-epoxypropylphosphonate + 2 H2O
• Cofactor: Fe cation

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

Key reference

DOI no: 10.1073/pnas.0504314102

Proc Natl Acad Sci U S A 102:14221-14226 (2005)

PubMed id: 16186494

Structure and reactivity of hydroxypropylphosphonic acid epoxidase in fosfomycin biosynthesis by a cation- and flavin-dependent mechanism.

K.McLuskey, S.Cameron, F.Hammerschmidt, W.N.Hunter.

ABSTRACT

The biosynthesis of fosfomycin, an oxirane antibiotic in clinical use, involves a unique epoxidation catalyzed by (S)-2-hydroxypropylphosphonic acid epoxidase (HPPE). The reaction is essentially dehydrogenation of a secondary alcohol. A high-resolution crystallographic analysis reveals that the HPPE subunit displays a two-domain combination. The C-terminal or catalytic domain has the cupin fold that binds a divalent cation, whereas the N-terminal domain carries a helix-turn-helix motif with putative DNA-binding helices positioned 34 A apart. The structure of HPPE serves as a model for numerous proteins, of ill-defined function, predicted to be transcription factors but carrying a cupin domain at the C terminus. Structure-reactivity analyses reveal conformational changes near the catalytic center driven by the presence or absence of ligand, that HPPE is a Zn(2+)/Fe(2+)-dependent epoxidase, proof that flavin mononucleotide is required for catalysis, and allow us to propose a simple mechanism that is compatible with previous experimental data. The participation of the redox inert Zn(2+) in the mechanism is surprising and indicates that Lewis acid properties of the metal ions are sufficient to polarize the substrate and, aided by flavin mononucleotide reduction, facilitate the epoxidation.

Selected figure(s)

Figure 2.
Fig. 2. Molecular structure. (a) Ribbon diagram of the HPPE subunit with helices colored red and strands, blue. Zn2+ is depicted as a sphere (magenta). (b) The functional tetramer viewed down a crystallographic twofold axis. Subunits are coloured red (A), blue (B), gold (C), and cyan (D). PYMOL (28) was used for molecular images.

Figure 4.
Fig. 4. A postulated mechanism for HPPE. States A and C are represented by the structures HPPE-Zn and HPPE-Fos, respectively.

Figures were selected by the author.

Author's comment

Another structure of this enzyme in the PDB (1zz8) has Fe(2+) in the active site and the mechanism proposed exploits the redox properties of the metal ion. In our study, we also showed that the enzyme was active with Zn(2+) suggesting that redox chemistry is not a requirement for function.

Bill Hunter