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|Title:||Density functional theory calculations on biological S-transfer: Insight into the mechanism of rhodanese|
|Keywords:||Density functional calculations|
|Abstract:||Biological sulfur transfer (S-transfer) is a key step in the synthesis of metabolites, CN<sup>-</sup> detoxification and assembly of iron-sulfur clusters. Computational results addressing the thermodynamics of the S-transfer reactions from thiosulfate (natural S-donor) to HCN and thiol are presented. These calculations indicate that S-transfer from thiosulfate to HCN and thiol is possible only in the anionic forms of these species. However these species have <i style="">pK</i><sub>a</sub> values significantly higher than physiological <i style="">p</i>H value (i.e., they are protonated in physiological <i style="">p</i>H and incapable of S-transfer). In the rhodanese active site, basic residues are present to deprotonate the catalytic cysteine group which accepts the S-atom from thiosulfate. The resultant perthiol species transfer S-atom to CN<sup>-</sup> in a synchronous S-atom and H<sup>+</sup> transfer step facilitated by the two arginine residues present in the rhodanese active site. Based on these calculations, a mechanism is proposed for the rhodanese catalyzed CN<sup>-</sup> detoxification pathway.|
|Appears in Collections:||IJC-A Vol.50A(09-10) [September-October 2011]|
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|IJCA 50A(09-10) 1457-1462.pdf||234.82 kB||Adobe PDF||View/Open|
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