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|Title:||Zn catalyzed alkyl-transfer reactions: A new class of biological Zn sites|
|Authors:||Penner-Hahn, James E|
|Abstract:||The use of X-ray absorption to characterize a novel class of Zn alkyl-transfer enzymes is illustrated, using examples taken from the recent literature, with emphasis on characterization of the Zn sites in the methionine synthase enzymes. By probing directly the structure of the Zn site, X-ray spectroscopy was used to demonstrate that Zn is intimately involved in the catalytic reaction of both the MetE and the MetH methionine synthases. From extended X-ray absorption fine structure (EXAFS) measurements, it is possible to demonstrate that thiolate-containing substrates bind directly to the Zn site. Although EXAFS is limited in its ability to characterize individual ligands, the combination of EXAFS with site directed mutagenesis is able to identify the specific amino acids that are bound to the Zn in methionine synthase. Recent results using X-ray absorption near edge structure (XANES) suggest intriguing geometrical difference between the Zn sites of related alkyl-transfer enzymes.|
|Appears in Collections:||IJC-A Vol.41A(01) [January 2002]|
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