S K-edge XAS and DFT calculations on SAM dependent pyruvate formate-lyase activating enzyme: nature of interaction between the Fe4S4 cluster and SAM and its role in reactivity.

ABSTRACT: 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 tran

SUBMITTER: Dey A 

PROVIDER: S-EPMC3235791 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature