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Humboldt-Universitaet zu Berlin - Structural Biology / Biochemistry

Humboldt-Universitaet zu Berlin | Department of Biology | Structural Biology / Biochemistry | Publications | New insights into the thermostability of bacterial ferredoxins: high-resolution crystal structure of the seven-iron ferredoxin from Thermus thermophilus.

Sandra Macedo-Ribeiro, Berta M Martins, Pedro J Pereira, G Buse, Robert Huber, and Tewfik Soulimane (2001)

New insights into the thermostability of bacterial ferredoxins: high-resolution crystal structure of the seven-iron ferredoxin from Thermus thermophilus.

Journal of Biological Inorganic Chemistry, 6(7):663-74.

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.