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191 a.a.
_HG
_ZN
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 withhelices 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
Literature references that cite this PDB file's key reference
PubMed id Reference
20179877 P.Domínguez de María, R.W.van Gemert, A.J.Straathof, and U.Hanefeld (2010).
Biosynthesis of ethers: unusual or common natural events?Nat Prod Rep, 27, 370-392.
19478949 G.Agarwal, M.Rajavel, B.Gopal, and N.Srinivasan (2009).
Structure-based phylogeny as a diagnostic for functional characterization of proteins with a cupin fold.PLoS One, 4, e5736.
19020684 P.C.Bruijnincx, G.van Koten, and R.J.Klein Gebbink (2008).
Mononuclear non-heme iron enzymes with the 2-His-1-carboxylate facial triad: recent developments in enzymology and modeling studies.Chem Soc Rev, 37, 2716-2744.
17220970 R.D.Woodyer, G.Li, H.Zhao, and W.A.van der Donk (2007).
New insight into the mechanism of methyl transfer during the biosynthesis of fosfomycin.Chem Commun (Camb), 0, 359-361. The most recent references are shown first. Citation data come partly from CiteXplore and partly from an automated harvesting procedure. Note that this is likely to be only a partial list as not all journals are covered by either method. However, we are continually building up the citation data so more and more references will be included with time.
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