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

TY - JOUR

T1 - Structure and reactivity of hydroxypropylphosphonic acid epoxidase in fosfomycin biosynthesis by a cation- and flavin-dependent mechanism

AU - McLuskey, Karen

AU - Cameron, Scott

AU - Hammerschmidt, Friedrich

AU - Hunter, William N.

A2 - Davies, David R.

N1 - dc.publisher: National Academy of Sciences dc.description.sponsorship: Biotechnology and Biological Sciences Research Council Wellcome Trust

PY - 2005/10

Y1 - 2005/10

N2 - 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 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.

AB - 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 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.

KW - Enzymes

KW - Epoxidation

KW - Iron

KW - Zinc

U2 - 10.1073/pnas.0504314102

DO - 10.1073/pnas.0504314102

M3 - Article

SN - 0027-8424

VL - 102

SP - 14221

EP - 14226

JO - Proceedings of the National Academy of Sciences of the United States of America

JF - Proceedings of the National Academy of Sciences of the United States of America

IS - 40

ER -