Mirror image mutations reveal the significance of an intersubunit ion cluster in the stability of 3‐isopropylmalate dehydrogenase

FEBS Letters

Gál, Péter¹  Svingor, Ádám¹  Szilágyi, András¹  Németh, Attila¹  Pócsik, Márta¹  Závodszky, Péter¹  Dobó, József¹  Magyar, Csaba¹ 

[1] Institute of Enzymology, Hungarian Academy of Sciences, P.O. Box 7, H-1518 Budapest, Hungary

关键词: 3-Isopropylmalate dehydrogenase;    Ion cluster;    Circular dichroism;    Differential scanning calorimetry;    Site-directed mutagenesis;    Thermostability;   

DOI  :  10.1016/S0014-5793(00)01190-X

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The comparison of the three-dimensional structures of thermophilic (Thermus thermophilus) and mesophilic (Escherichia coli) 3-isopropylmalate dehydrogenases (IPMDH, EC 1.1.1.85) suggested that the existence of extra ion pairs in the thermophilic enzyme found in the intersubunit region may be an important factor for thermostability. As a test of our assumption, glutamine 200 in the E. coli enzyme was turned into glutamate (Q200E mutant) to mimic the thermophilic enzyme at this site by creating an intersubunit ion pair which can join existing ion clusters. At the same site in the thermophilic enzyme we changed glutamate 190 into glutamine (E190Q), hereby removing the corresponding ion pair. These single amino acid replacements resulted in increased thermostability of the mesophilic and decreased thermostability of the thermophilic enzyme, as measured by spectropolarimetry and differential scanning microcalorimetry.

【 授权许可】

Unknown