Open AccessSulfur K-Edge XAS Studies of the Effect of DNA Binding on the [Fe4S4] Site in EndoIII and MutY
Author(s) -
Yang Ha,
Anna R. Arnold,
Nicole N. Nuñez,
Phillip L. Bartels,
Andy Zhou,
Sheila S. David,
Jacqueline K. Barton,
Britt Hedman,
Keith O. Hodgson,
Edward I. Solomon
Publication year - 2017
Publication title -
journal of the american chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.115
H-Index - 612
eISSN - 1520-5126
pISSN - 0002-7863
DOI - 10.1021/jacs.7b03966
Subject(s) - chemistry , x ray absorption spectroscopy , ferredoxin , solvation , sulfur , redox , crystallography , valence (chemistry) , sulfide , inorganic chemistry , absorption spectroscopy , solvent , enzyme , biochemistry , organic chemistry , physics , quantum mechanics
S K-edge X-ray absorption spectroscopy (XAS) was used to study the [Fe 4 S 4 ] clusters in the DNA repair glycosylases EndoIII and MutY to evaluate the effects of DNA binding and solvation on Fe-S bond covalencies (i.e., the amount of S 3p character mixed into the Fe 3d valence orbitals). Increased covalencies in both iron-thiolate and iron-sulfide bonds would stabilize the oxidized state of the [Fe 4 S 4 ] clusters. The results are compared to those on previously studied [Fe 4 S 4 ] model complexes, ferredoxin (Fd), and to new data on high-potential iron-sulfur protein (HiPIP). A limited decrease in covalency is observed upon removal of solvent water from EndoIII and MutY, opposite to the significant increase observed for Fd, where the [Fe 4 S 4 ] cluster is solvent exposed. Importantly, in EndoIII and MutY, a large increase in covalency is observed upon DNA binding, which is due to the effect of its negative charge on the iron-sulfur bonds. In EndoIII, this change in covalency can be quantified and makes a significant contribution to the observed decrease in reduction potential found experimentally in DNA repair proteins, enabling their HiPIP-like redox behavior.