1ebg
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(New page: 200px<br /><applet load="1ebg" size="450" color="white" frame="true" align="right" spinBox="true" caption="1ebg, resolution 2.1Å" /> '''CHELATION OF SER 39 T...)
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Revision as of 11:45, 20 November 2007
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CHELATION OF SER 39 TO MG2+ LATCHES A GATE AT THE ACTIVE SITE OF ENOLASE: STRUCTURE OF THE BIS(MG2+) COMPLEX OF YEAST ENOLASE AND THE INTERMEDIATE ANALOG PHOSPHONOACETOHYDROXAMATE AT 2.1 ANGSTROMS RESOLUTION
Overview
The structure of a new crystal form of enolase from bakers' yeast has been, solved to 2.1-A resolution. Crystals were grown from poly(ethylene glycol), and KCl at pH 8.2 in the presence of Mg2+ and a reaction intermediate, analog, phosphonoacetohydroxamate (PhAH). Crystals belong to space group, C2; have unit cell dimensions a = 123.5 A, b = 73.9 A, and c = 94.8 A with, beta = 93.3 degrees; and contain one dimer per asymmetric unit. The, structure was solved by molecular replacement from the X-ray coordinates, of apoenolase [Stec, B., & Lebioda, L. (1990) J. Mol. Biol. 211, 235-248]., Both essential divalent metal ions are observed to be complexed with the, inhibitor. The two Mg2+ ions are 4.05 A apart and are bridged by a mu-oxyl, ligand from the carbonyl moiety of PhAH. The "high-affinity" Mg2+, coordinates to the carboxylate side chains of Asp 246, Glu 295, and Asp, 320, one water molecule, and the hydroxamate and carbonyl oxygens of PhAH., The second Mg2+ coordinates to a phosphonyl oxygen, two water molecules, and the mu-bridge carbonyl oxygen of PhAH. Coordination schemes with, respect to PhAH and water ligands are fully consistent with those of the, Mn2+ complexes determined spectroscopically [Poyner, R.R., & Reed, G. H., (1992) Biochemistry 31, 7166-7173]. Remaining ligands for the second Mg2+, are the carbonyl oxygen and gamma-oxygen of Ser 39. Chelation of this Ser, residue to Mg2+ effectively "latches" a flexible loop extending from Gly, 37 through His 43 and closes off the entrance to the active site. The, position of the second Mg2+ in the active site provides new insight into, the stereochemistry of substrate binding.
About this Structure
1EBG is a Single protein structure of sequence from Saccharomyces cerevisiae with MG and PAH as ligands. Active as Phosphopyruvate hydratase, with EC number 4.2.1.11 Full crystallographic information is available from OCA.
Reference
Chelation of serine 39 to Mg2+ latches a gate at the active site of enolase: structure of the bis(Mg2+) complex of yeast enolase and the intermediate analog phosphonoacetohydroxamate at 2.1-A resolution., Wedekind JE, Poyner RR, Reed GH, Rayment I, Biochemistry. 1994 Aug 9;33(31):9333-42. PMID:8049235
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