Sequence, assembly and evolution of a primordial ferredoxin from Thermotoga maritima.
A gene coding for the ferredoxin of the primordial, strictly anaerobic and hyperthermophilic bacterium Thermotoga maritima was cloned, sequenced and expressed in Escherichia coli. The ferredoxin gene encodes a polypeptide of 60 amino acids that incorporates a single 4Fe-4S cluster. T. maritima ferredoxin expressed in E. coli is a heat-stable, monomeric protein, the spectroscopic properties of which show that its 4Fe-4S cluster is correctly assembled within the mesophilic host, and that it remains stable during purification under aerobic conditions. Removal of the iron-sulfur cluster results in an apo-ferredoxin that has no detectable secondary structure. This observation indicates that in vivo formation of the ferredoxin structure is coupled to the insertion of the iron-sulfur cluster into the polypeptide chain. Sequence comparison of T. maritima ferredoxin with other 4Fe-4S ferredoxins revealed high sequence identities (75% and 50% respectively) to the ferredoxins from the hyperthermophilic members of the Archaea, Thermococcus litoralis and Pyrococcus furiosus. The high sequence similarity supports a close relationship between these extreme thermophilic organisms from different phylogenetic domains and suggests that ferredoxins with a single 4Fe-4S cluster are the primordial representatives of the whole protein family. This observation suggests a new model for the evolution of ferredoxins.
Darimont
B
B
Department of Biophysical Chemistry, University of Basel, Switzerland.
Sterner
R
R
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D005075:Biological Evolution; D002942:Circular Dichroism; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D005288:Ferredoxins / Q000235:genetics* / Q000378:metabolism; D005798:Genes, Bacterial / Q000235:genetics; D006089:Gram-Negative Anaerobic Bacteria / Q000235:genetics*; D007501:Iron / Q000378:metabolism; D008957:Models, Genetic; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000096:biosynthesis; D017386:Sequence Homology, Amino Acid; D013056:Spectrophotometry, Ultraviolet; D013455:Sulfur / Q000378:metabolism
D001426:Bacterial Proteins; D005288:Ferredoxins; D011994:Recombinant Proteins; D013455:Sulfur; D007501:Iron