title: Atomic resolution structures of rieske iron-sulfur protein: role of hydrogen bonds in tuning the redox potential of iron-sulfur clusters.
abstract: The Rieske [2Fe-2S] iron-sulfur protein of cytochrome bc(1) functions as the initial electron acceptor in the rate-limiting step of the catalytic reaction. Prior studies have established roles for a number of conserved residues that hydrogen bond to ligands of the [2Fe-2S] cluster. We have constructed site-specific variants at two of these residues, measured their thermodynamic and functional properties, and determined atomic resolution X-ray crystal structures for the native protein at 1.2 A resolution and for five variants (Ser-154-->Ala, Ser-154-->Thr, Ser-154-->Cys, Tyr-156-->Phe, and Tyr-156-->Trp) to resolutions between 1.5 A and 1.1 A. These structures and complementary biophysical data provide a molecular framework for understanding the role hydrogen bonds to the cluster play in tuning thermodynamic properties, and hence the rate of this bioenergetic reaction. These studies provide a detailed structure-function dissection of the role of hydrogen bonds in tuning the redox potentials of [2Fe-2S] clusters.
authors.affiliation: Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, 600 S. Mathews Avenue, Urbana, IL 61801, USA.
authors.forename: Derrick J
authors.initials: DJ
authors.lastname: Kolling
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Brunzelle
authors.forename: Sangmoon
authors.initials: S
authors.lastname: Lhee
authors.forename: Antony R
authors.initials: AR
authors.lastname: Crofts
authors.forename: Satish K
authors.initials: SK
authors.lastname: Nair
mesh_terms: D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D018360:Crystallography, X-Ray; D014450:Electron Transport Complex III / Q000737:chemistry* / Q000235:genetics; D006860:Hydrogen Bonding; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000235:genetics; D009154:Mutation; D010084:Oxidation-Reduction; D011487:Protein Conformation; D012242:Rhodobacter sphaeroides / Q000378:metabolism*; D012694:Serine / Q000737:chemistry / Q000235:genetics; D013329:Structure-Activity Relationship; D014443:Tyrosine / Q000737:chemistry / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D007506:Iron-Sulfur Proteins; C037989:Rieske iron-sulfur protein; D014443:Tyrosine; D012694:Serine; D014450:Electron Transport Complex III