Iron-sulfur proteins are ubiquitous in nature and occur in most metabolic pathways, and an understanding of the parameters determining their physico-chemical properties is a central problem of biochemistry. Among the most interesting are the 2Fe-2S clusters that have as a common feature the liganding of the irons by two cysteines and two histidines. These include the Rieske iron-sulfur protein (ISP) of the bc1 (and related) complexes, and several Rieske-type bacterial proteins, including the archaeal sulredoxin (SDX) of Sulfolobus sp. Strain 7 and Rieske-type ferredoxin (ARF) from S. solfaricus to be investigated in this project. A remarkable feature of these proteins is the wide variation in redox potentials, from -100 to 300 mV, exhibited by the 2Fe-2S clusters, despite their similar ligation. Recent crystallographic structures show a similar orientation of ligands in the cluster binding domain in proteins at both extremes of this range. This implies that the redox potentials and protolytic properties of each particular cluster are controlled by other unique features of the protein environment. To understand how the proteins function, the factors influencing these parameters must be determined at the atomic level for each protein. We propose to investigate the protein environment of the three Rieske-type clusters above by using advanced magnetic resonance techniques, with an emphasis on 2-D ESEEM to explore the interaction between the paramagnetic centers and nuclear spins in the neighborhood. We will analyze the data so as to provide structural information, and compared this with the crystallographic structured of ISP, and of naphthalene- 1,2-dioxygenase. The spectroscopic results will provide constraints to allow precise determination of the cluster environment including coordination of histidine and cysteine ligands, presence of hydrogen bonds and non-coordinated nitrogens, and accessibility of solvent. By performing similar experiments with mutant strains generated by molecular engineering, we anticipate that we will be able to identify the local features of the protein environment that control the redox and protolytic properties of the clusters, their role in reaction mechanisms, and the changes that produce functional modification in different strains. The results will answer some fundamental questions about structural factors controlling the redox potentials of Rieske-type proteins, and provide insights to similar questions in other redox proteins.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM062954-02
Application #
6621664
Study Section
Metallobiochemistry Study Section (BMT)
Program Officer
Preusch, Peter C
Project Start
2002-03-01
Project End
2007-02-28
Budget Start
2003-03-01
Budget End
2004-02-29
Support Year
2
Fiscal Year
2003
Total Cost
$225,241
Indirect Cost
Name
University of Illinois Urbana-Champaign
Department
Veterinary Sciences
Type
Schools of Veterinary Medicine
DUNS #
041544081
City
Champaign
State
IL
Country
United States
Zip Code
61820
Taguchi, Alexander T; O'Malley, Patrick J; Wraight, Colin A et al. (2014) Hyperfine and nuclear quadrupole tensors of nitrogen donors in the Q(A) site of bacterial reaction centers: correlation of the histidine N(?) tensors with hydrogen bond strength. J Phys Chem B 118:9225-37
Taguchi, Alexander T; O'Malley, Patrick J; Wraight, Colin A et al. (2014) Nuclear hyperfine and quadrupole tensor characterization of the nitrogen hydrogen bond donors to the semiquinone of the QB site in bacterial reaction centers: a combined X- and S-band (14,15)N ESEEM and DFT study. J Phys Chem B 118:1501-9
Hong, Sangjin; de Almeida, Wagner B; Taguchi, Alexander T et al. (2014) The semiquinone at the Qi site of the bc1 complex explored using HYSCORE spectroscopy and specific isotopic labeling of ubiquinone in Rhodobacter sphaeroides via (13)C methionine and construction of a methionine auxotroph. Biochemistry 53:6022-31
Taguchi, Alexander T; Mattis, Aidas J; O'Malley, Patrick J et al. (2013) Tuning cofactor redox potentials: the 2-methoxy dihedral angle generates a redox potential difference of >160 mV between the primary (Q(A)) and secondary (Q(B)) quinones of the bacterial photosynthetic reaction center. Biochemistry 52:7164-6
Crofts, Antony R; Hong, Sangjin; Wilson, Charles et al. (2013) The mechanism of ubihydroquinone oxidation at the Qo-site of the cytochrome bc1 complex. Biochim Biophys Acta 1827:1362-77
Victoria, Doreen; Burton, Rodney; Crofts, Antony R (2013) Role of the -PEWY-glutamate in catalysis at the Q(o)-site of the Cyt bc(1) complex. Biochim Biophys Acta 1827:365-86
Taguchi, Alexander T; O'Malley, Patrick J; Wraight, Colin A et al. (2013) Conformational differences between the methoxy groups of QA and QB site ubisemiquinones in bacterial reaction centers: a key role for methoxy group orientation in modulating ubiquinone redox potential. Biochemistry 52:4648-55
Xue, Bo; Chow, Jeng Yeong; Baldansuren, Amgalanbaatar et al. (2013) Structural evidence of a productive active site architecture for an evolved quorum-quenching GKL lactonase. Biochemistry 52:2359-70
Maklashina, Elena; Cecchini, Gary; Dikanov, Sergei A (2013) Defining a direction: electron transfer and catalysis in Escherichia coli complex II enzymes. Biochim Biophys Acta 1827:668-78
Dikanov, Sergei A; Liboiron, Barry D; Orvig, Chris (2013) VO(2+)-hydroxyapatite complexes as models for vanadyl coordination to phosphate in bone. Mol Phys 111:2967-2979

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