Abstract
S K-edge X-ray absorption spectroscopy (XAS) was used to study the [Fe4S4] 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 [Fe4S4] clusters. The results are compared to those on previously studied [Fe4S4] 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 [Fe4S4] 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.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Bacteria / chemistry
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Bacteria / enzymology
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Bacteria / metabolism
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Bacterial Proteins / chemistry
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Bacterial Proteins / metabolism
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Binding Sites
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DNA / metabolism*
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DNA Glycosylases / chemistry
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DNA Glycosylases / metabolism*
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Deoxyribonuclease (Pyrimidine Dimer) / chemistry
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Deoxyribonuclease (Pyrimidine Dimer) / metabolism*
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Escherichia coli / chemistry
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Escherichia coli / enzymology*
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Escherichia coli / metabolism
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Escherichia coli Proteins / chemistry
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Escherichia coli Proteins / metabolism*
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Geobacillus stearothermophilus / chemistry
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Geobacillus stearothermophilus / enzymology*
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Geobacillus stearothermophilus / metabolism
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Iron-Sulfur Proteins / chemistry
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Iron-Sulfur Proteins / metabolism
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Models, Molecular
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Photosynthetic Reaction Center Complex Proteins / chemistry
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Photosynthetic Reaction Center Complex Proteins / metabolism
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Protein Binding
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X-Ray Absorption Spectroscopy / methods
Substances
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Bacterial Proteins
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Escherichia coli Proteins
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Iron-Sulfur Proteins
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Photosynthetic Reaction Center Complex Proteins
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high potential iron-sulfur protein
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DNA
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Deoxyribonuclease (Pyrimidine Dimer)
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NTH protein, E coli
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DNA Glycosylases
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mutY adenine glycosylase