3pfl: Difference between revisions

[[Image:3pfl.jpg|left|200px]]<br /><applet load="3pfl" size="350" color="white" frame="true" align="right" spinBox="true"  

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.

3PFL is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with <scene name='pdbligand=OXM:'>OXM</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Formate_C-acetyltransferase Formate C-acetyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.3.1.54 2.3.1.54] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=3PFL OCA].  

[[Category: Wagner, A F.V.]]

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