title: Ferredoxin from the hyperthermophile Thermotoga maritima is stable beyond the boiling point of water.
abstract: Heat-stable proteins from hyperthermophilic microorganisms are ideally suited for investigating protein stability and evolution. We measured with differential scanning calorimetry and optical absorption spectroscopy the thermal stability of [4Fe-4S] ferredoxin from Thermotoga maritima (tfdx), which is a small electron transfer protein. The results are consistent with two-state unfolding at the record denaturation temperature of 125 degrees C. According to the crystal structure at 1.75 A resolution, T. maritima ferredoxin contains a significantly increased number of hydrogen bonds that involve charged amino acid side-chains, compared to thermolabile ferredoxins. Thus, our results suggest that polar interactions substantially contribute to protein stability at very high temperatures. Moreover, because small [4Fe-4S] ferredoxins seem to have occurred early in evolution, the extreme thermostability of tfdx supports the hypothesis that life originated at high temperatures.
authors.affiliation: Analytische Biochemie, Universität Potsdam, c./o. Max-Delbrück-Centrum für molekulare Medizin, Robert-Rössle-Strasse 10, Berlin, D-13122, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Pfeil
authors.forename: U
authors.initials: U
authors.lastname: Gesierich
authors.forename: G R
authors.initials: GR
authors.lastname: Kleemann
authors.forename: R
authors.initials: R
authors.lastname: Sterner
mesh_terms: D002152:Calorimetry, Differential Scanning; D005288:Ferredoxins / Q000737:chemistry*; D016965:Gram-Negative Anaerobic Straight, Curved, and Helical Rods / Q000737:chemistry*; D006358:Hot Temperature; D017510:Protein Folding; D014867:Water / Q000737:chemistry
chemical_list: D005288:Ferredoxins; D014867:Water