| Autor: |
Dey A; Department of Chemistry, Stanford University, Stanford, California 94305, USA., Peng Y, Broderick WE, Hedman B, Hodgson KO, Broderick JB, Solomon EI |
| Jazyk: |
angličtina |
| Zdroj: |
Journal of the American Chemical Society [J Am Chem Soc] 2011 Nov 23; Vol. 133 (46), pp. 18656-62. Date of Electronic Publication: 2011 Oct 28. |
| DOI: |
10.1021/ja203780t |
| Abstrakt: |
S K-edge X-ray absorption spectroscopy on the resting oxidized and the S-adenosyl-l-methionine (SAM) bound forms of pyruvate formate-lyase activating enzyme are reported. The data show an increase in pre-edge intensity, which is due to additional contributions from sulfide and thiolate of the Fe(4)S(4) cluster into the C-S σ* orbital. This experimentally demonstrates that there is a backbonding interaction between the Fe(4)S(4) cluster and C-S σ* orbitals of SAM in this inner sphere complex. DFT calculations that reproduce the data indicate that this backbonding is enhanced in the reduced form and that this configurational interaction between the donor and acceptor orbitals facilitates the electron transfer from the cluster to the SAM, which otherwise has a large outer sphere electron transfer barrier. The energy of the reductive cleavage of the C-S bond is sensitive to the dielectric of the protein in the immediate vicinity of the site as a high dielectric stabilizes the more charge separated reactant increasing the reaction barrier. This may provide a mechanism for generation of the 5'-deoxyadenosyl radical upon substrate binding. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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