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S. Kardinahl, S. Anemüller, G. Schäfer
The Hyper-Thermostable Fe-Superoxide Dismutase from the Archaeon Acidianus ambivalens: Characterization, Recombinant Expression, Crystallization and Effects of Metal Exchange
An iron-containing superoxide dismutase (SOD; EC
1.15.1.1) of the hyperthermophilic archaeon
Both, the native as well as the heterologously overproduced
protein turned out to have extraordinarily
high melting temperatures of 128 °C and 124.5 °C, respectively.
To the best of our knowledge, this is the
highest directly measured melting temperature of a
native protein. Surprisingly, neither the native nor the
recombinant superoxide dismutase displays 100%
occupation of the metal coordination sites. Obviously
it is not the incorporation of a metal ion that confers
the extreme thermostability. Expression of the superoxide
dismutase in the presence of different metals
such as Fe, Co, Ni, Mn and Cu offered the possibility of
studying the hitherto unknown cofactor preference of
iron-superoxide dismutase. The recombinant enzyme
displayed the highest preference for incorporation of
cobalt although iron is used as the natural cofactor.
Spectroscopic analysis by EPR, atomic absorption
and UV/Vis spectroscopy as well as activity measurements
and differential scanning calorimetry of the
metal substituted superoxide dismutases were performed.
However, the superoxide dismutase of
Biological Chemistry, Walter de Gruyter
Print ISSN: 1431-6730
Volume: 381, 11/2000
Pages: 1089 - 1101