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Structure and mechanism of the glycyl radical enzyme pyruvate formate-lyase

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Becker,  Andreas
Emeritus Group Biophysics, Max Planck Institute for Medical Research, Max Planck Society;

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Kabsch,  Wolfgang
Emeritus Group Biophysics, Max Planck Institute for Medical Research, Max Planck Society;
Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Max Planck Society;

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Citation

Becker, A., Fritz−Wolf, K., Kabsch, W., Knappe, J., Schultz, S., & Wagner, A. F. V. (1999). Structure and mechanism of the glycyl radical enzyme pyruvate formate-lyase. Nature structural biology, 6(10), 969-975. doi:10.1038/13341.


Cite as: http://hdl.handle.net/21.11116/0000-0000-405D-0
Abstract
Pyruvate formate-lyase (PFL) from Escherichia coli uses a radical mechanism to reversibly cleave the C1-C2 bond of pyruvate using the Gly 734 radical and two cysteine residues (Cys 418, Cys 419). We have determined by X-ray crystallography the structures of PFL (non-radical form), its complex with the substrate analog oxamate, and the C418A,C419A double mutant. The atomic model (a dimer of 759-residue monomers) comprises a 10-stranded beta/alpha barrel assembled in an antiparallel manner from two parallel five-stranded beta-sheets; this architecture resembles that of ribonucleotide reductases. Gly 734 and Cys 419, positioned at the tips of opposing hairpin loops, meet in the apolar barrel center (Calpha-Sgamma = 3.7 A). Oxamate fits into a compact pocket where C2 is juxtaposed with Cys 418Sgamma (3.3 A), which in turn is close to Cys 419Sgamma (3.7 A). Our model of the active site is suggestive of a snapshot of the catalytic cycle, when the pyruvate-carbonyl awaits attack by the Cys 418 thiyl radical. We propose a homolytic radical mechanism for PFL that involves Cys 418 and Cys 419 both as thiyl radicals, with distinct chemical functions.