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

Karen McLuskey, Scott Cameron, Friedrich Hammerschmidt, William N. Hunter*

*Corresponding author for this work

    Research output: Contribution to journalArticle

    26 Citations (Scopus)

    Abstract

    The biosynthesis of fosfomycin, an oxirane antibiotic in clinical use, involves a unique epoxidation catalyzed by (5)-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 Å 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 Zn2+/Fe2+-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 Zn2+ 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.

    Original languageEnglish
    Pages (from-to)14221-14226
    Number of pages6
    JournalProceedings of the National Academy of Sciences of the United States of America
    Volume102
    Issue number40
    DOIs
    Publication statusPublished - 4 Oct 2005

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