METALLOENZYMES AND MEDICINE

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The biosynthetic pathway of the clinically important antibiotic fosfomycin uses enzymes that catalyse reactions without precedent in biology. Among these is hydroxypropylphosphonic acid epoxidase, which represents a new subfamily of non-haem mononuclear iron enzymes. Here we present six X-ray structures of this enzyme: the apoenzyme at 2.0 A resolution; a native Fe(II)-bound form at 2.4 A resolution; a tris(hydroxymethyl)aminomethane-Co(II)-enzyme complex structure at 1.8 A resolution; a substrate-Co(II)-enzyme complex structure at 2.5 A resolution; and two substrate-Fe(II)-enzyme complexes at 2.1 and 2.3 A resolution. These structural data lead us to suggest how this enzyme is able to recognize and respond to its substrate with a conformational change that protects the radical-based intermediates formed during catalysis. Comparisons with other family members suggest why substrate binding is able to prime iron for dioxygen binding in the absence of alpha-ketoglutarate (a co-substrate required by many mononuclear iron enzymes), and how the unique epoxidation reaction of hydroxypropylphosphonic acid epoxidase may occur. This work was published in Nature, with five of the deposited PDB codes (1ZZ6, 1ZZ9, 1ZZ7 1ZZC, 1ZZB) coming from data taken at NE-CAT 8-BM.