Ferredoxin from the hyperthermophile Thermotoga maritima is stable beyond the boiling point of water.
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.[1]References
- Ferredoxin from the hyperthermophile Thermotoga maritima is stable beyond the boiling point of water. Pfeil, W., Gesierich, U., Kleemann, G.R., Sterner, R. J. Mol. Biol. (1997) [Pubmed]
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