title: Crystal structure of Escherichia coli Fdx, an adrenodoxin-type ferredoxin involved in the assembly of iron-sulfur clusters.
abstract: Escherichia coli ferredoxin (Fdx) is an adrenodoxin-type [2Fe-2S] ferredoxin. Recent genetic analyses show that it has an essential role in the maturation of various iron-sulfur (Fe-S) proteins. Fdx probably functions as a component of the complex machinery responsible for the biogenesis of Fe-S clusters. Its crystal structure was determined by the multiple-wavelength anomalous dispersion method using the iron atoms in the [2Fe-2S] cluster of the protein and then refined to R and R(free) values of 0.255 and 0.278, respectively, at 1.7 A resolution. The structure of Fdx is similar to the structures of bovine adrenodoxin (Adx) and Pseudomonas putida putidaredoxin (Pdx) whose respective root-mean-square deviations of the corresponding Calpha atoms are 1.8 and 2.2 A. This analysis also revealed the structure of the C-terminal residues protruding into the solvent, which is missing in Adx and Pdx. The [2Fe-2S] cluster is located at the edge of the molecule and bonds with the Sgamma atoms of Cys42, Cys48, Cys51, and Cys87. Electrostatic potential analysis showed that the surface of Fdx has two negatively charged areas separated by a hydrophobic lane. One is conserved on the surface of Adx which is an area of interaction with adrenodoxin reductase. Cys46 is located on the molecular surface in the vicinity of the [2Fe-2S] cluster, an indication that it may be involved in Fe-S cluster formation.
authors.affiliation: Department of Biology, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Kakuta
authors.forename: T
authors.initials: T
authors.lastname: Horio
authors.forename: Y
authors.initials: Y
authors.lastname: Takahashi
authors.forename: K
authors.initials: K
authors.lastname: Fukuyama
mesh_terms: D000325:Adrenodoxin / Q000737:chemistry; D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D004579:Electron Transport; D004926:Escherichia coli / Q000737:chemistry*; D005288:Ferredoxins / Q000737:chemistry*; D007501:Iron / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000096:biosynthesis; D008958:Models, Molecular; D008969:Molecular Sequence Data; D055672:Static Electricity; D013455:Sulfur / Q000378:metabolism
chemical_list: C081714:2Fe-2S ferredoxin; D005288:Ferredoxins; D007506:Iron-Sulfur Proteins; D000325:Adrenodoxin; C100137:putidaredoxin; D013455:Sulfur; D007501:Iron