Sarangi, Ritimukta, Hocking, Rosalie K., Neidig, Michael L., Benfatto, Maurizio, Holman, Theodore R., Solomon, Edward I., Hodgson, Keith O., and Hedman, Britt (2008) Geometric structure determination of N694C lipoxygenase: a comparative near-edge X-ray absorption spectroscopy and extended X-ray absorption fine structure study. Inorganic Chemistry, 47 (24). pp. 11543-11550.

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Abstract

The mononuclear nonheme iron active site of N694C soybean lipoxygenase (sLO1) has been investigated in the resting ferrous form using a combination of Fe-K-pre-edge, near-edge (using the minuit X-ray absorption near-edge full multiple-scattering approach), and extended X-ray absorption fine structure (EXAFS) methods. The results indicate that the active site is six-coordinate (6C) with a large perturbation in the first-shell bond distances in comparison to the more ordered octahedral site in wild-type sLO1. Upon mutation of the asparigine to cystiene, the short Fe-O interaction with asparigine is replaced by a weak Fe-(H₂O), which leads to a distorted 6C site with an effective 5C ligand field. In addition, it is shown that near-edge multiple scattering analysis can give important three-dimensional structural information, which usually cannot be accessed using EXAFS analysis. It is further shown that; relative to EXAFS, near-edge analysis is more sensitive to partial coordination numbers and can be potentially used as a tool for structure determination in a mixture of chemical species.

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