title: New insights into the thermostability of bacterial ferredoxins: high-resolution crystal structure of the seven-iron ferredoxin from Thermus thermophilus.
abstract: The crystal structure of the seven-iron ferredoxin from Thermus thermophilus (FdTt) has been determined at 1.64 A resolution, allowing us to unveil the common mechanisms of thermostabilization within "bacterial-type" ferredoxins. FdTt and other homologous thermophilic seven-iron ferredoxins are smaller than their mesophilic counterparts. Thermostabilizing features are optimized in a minimal structural and functional unit, with an extensive cross-linking of secondary structure elements mediated by improved polar and hydrophobic interactions. Most of the potentially stabilizing features are focused on the vicinity of the functional [3Fe-4S] cluster. The structural [4Fe-4S] cluster is shielded in thermophilic FdTt by an increased number of polar interactions involving the two N-terminal residues. Comparisons with the hyperthermostable ferredoxin from Thermotoga maritima reveal that (1) a reduction in the number of non-glycine residues in strained conformations, (2) improved polar interactions within the common iron-sulfur cluster binding (betaalphabeta)2 motif, and (3) an optimized charge distribution at the protein surface, constitute a common strategy for increasing the thermal stability of these ferredoxins.
authors.affiliation: Max-Planck-Institut für Biochemie, Abteilung Strukturforschungm, Martinsried, Germany. sandra@aramis.ibmc.up.pt
authors.forename: S
authors.initials: S
authors.lastname: Macedo-Ribeiro
authors.forename: B M
authors.initials: BM
authors.lastname: Martins
authors.forename: P J
authors.initials: PJ
authors.lastname: Pereira
authors.forename: G
authors.initials: G
authors.lastname: Buse
authors.forename: R
authors.initials: R
authors.lastname: Huber
authors.forename: T
authors.initials: T
authors.lastname: Soulimane
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D018360:Crystallography, X-Ray; D005288:Ferredoxins / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D016963:Thermus thermophilus / Q000737:chemistry*
chemical_list: D005288:Ferredoxins