title: Calculation of the redox potentials of iron-sulfur proteins: the 2-/3-couple of [Fe4S*4Cys4] clusters in Peptococcus aerogenes ferredoxin, Azotobacter vinelandii ferredoxin I, and Chromatium vinosum high-potential iron protein.
abstract: Calculations of the redox potentials of the 2-/3-couples of [Fe4S*4Cys4] clusters in the iron-sulfur proteins Peptococcus aerogenes ferredoxin (PaFd), Azotobacter vinelandii ferredoxin I (AvFdI) and Chromatium vinosum high potential iron protein (CvHiPIP) based on the Protein Dipoles Langevin Dipoles (PDLD) method are reported. The structures of these proteins have been determined by X-ray crystallography; in the case of PaFd the structure has recently been revised due to a change in the sequence close to Cluster II. The large differences between the potentials of the [Fe4S*4Cys4] clusters of PaFd and AvFdI and the potential of the [Fe4S*4Cys4] cluster of CvHiPIP are successfully modeled and originate principally in differences in the configuration of main-chain amide groups near the clusters. The small difference between the potentials of PaFd and AvFdI is also satisfactorily modeled in the case of Cluster I of PaFd. Solvent dipoles close to the cluster in PaFd are an important contributor to its higher potential. The two X-ray structures of PaFd yield similar results for Cluster I of PaFd. In contrast, the results for Cluster II differ substantially; for reasons not yet clear, the recently revised structure leads to results in worse agreement with experiment.
authors.affiliation: Department of Chemistry, University of Southern California, Los Angeles 90089.
authors.forename: G M
authors.initials: GM
authors.lastname: Jensen
authors.forename: A
authors.initials: A
authors.lastname: Warshel
authors.forename: P J
authors.initials: PJ
authors.lastname: Stephens
mesh_terms: D000595:Amino Acid Sequence; D016948:Azotobacter vinelandii / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry; D002844:Chromatium / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005288:Ferredoxins / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010460:Peptococcus / Q000737:chemistry*; D045322:Photosynthetic Reaction Center Complex Proteins
chemical_list: D001426:Bacterial Proteins; D005288:Ferredoxins; D007506:Iron-Sulfur Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; C007943:high potential iron-sulfur protein