Mutational effects on thermostable superoxide dismutase from Aquifex pyrophilus: understanding the molecular basis of protein thermostability.
We designed two mutants of superoxide dismutase (SOD), one is thermostable and the other is thermolabile, which provide valuable insight to identify amino acid residues essential for the thermostability of the SOD from Aquifex pyrophilus (ApSOD). The mutant K12A, in which Lys12 was replaced by Ala, had increased thermostability compared to that of the wild type. The T(1/2) value of K12A was 210 min and that of the wild type was 175 min at 95 degrees C. However, the thermostability of the mutant E41A, which has a T(1/2) value of 25 min at 95 degrees C, was significantly decreased compared to the wild type of ApSOD. To explain the enhanced thermostability of K12A and thermolabile E41A on the structural basis, the crystal structures of the two SOD mutants have been determined. The results have clearly shown the general significance of hydrogen bonds and ion-pair network in the thermostability of proteins.
Lim
J H
JH
Structural Biology Research Center, Korea Institute of Science and Technology, Seoul 130-650, Korea.
Hwang
K Y
KY
Choi
J
J
Lee
D Y
DY
Ahn
B Y
BY
Cho
Y
Y
Kim
K S
KS
Han
Y S
YS
D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics*; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D004795:Enzyme Stability; D006860:Hydrogen Bonding; D008958:Models, Molecular; D009154:Mutation; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000235:genetics*; D013696:Temperature
D001426:Bacterial Proteins; D013482:Superoxide Dismutase