Three-dimensional structure of a highly thermostable enzyme, 3-isopropylmalate dehydrogenase of Thermus thermophilus at 2.2 A resolution.Imada, K., Sato, M., Tanaka, N., Katsube, Y., Matsuura, Y., Oshima, T.
(1991) J.Mol.Biol. 222: 725-738
- PubMed: 1748999
- PubMed Abstract:
- Purification, Catalytic Properties and Thermal Stability of Threo-Ds-3-Isopropylmalate Dehydrogenase Coded by Leub Gene from an Extreme Thermophile, Thermus Thermophilus Strain Hb8
Yamada, T.,Akutsu, N.,Miyazaki, K.,Kakinuma, K.,Yoshida, M.,Oshima, T.
(1990) J.Biochem.(Tokyo) 108: 449
- Crystallization and Preliminary X-Ray Data for 3-Isopropylmalate Dehydrogenase of Thermus Thermophilus
Katsube, Y.,Tanaka, N.,Takenaka, A.,Yamada, T.,Oshima, T.
(1988) J.Biochem.(Tokyo) 104: 679
The three-dimensional structure of the highly thermostable 3-isopropylmalate dehydrogenase (IPMDH) from Thermus thermophilus has been determined by the multiple isomorphous replacement method and refined to 2.2 A resolution. The final R-factor is 0.1 ...
The three-dimensional structure of the highly thermostable 3-isopropylmalate dehydrogenase (IPMDH) from Thermus thermophilus has been determined by the multiple isomorphous replacement method and refined to 2.2 A resolution. The final R-factor is 0.185 for 20,307 reflections. The crystal asymmetric unit has one subunit consisting of 345 amino acid residues. The polypeptide chain of this subunit is folded into two domains (first and second domains) with parallel alpha/beta motifs. The domains are similar in their conformations and folding topologies, but differ from those of the NAD-binding domains of such well-known enzymes as the alcohol and lactate dehydrogenases. A beta-strand that is a part of the long arm-like polypeptide protruding from the second domain comes into contact with another subunit and contributes to the formation of an isologous dimer with a crystallographic 2-fold symmetry. Close subunit contacts are also present at two alpha-helices in the second domain. These helices strongly interact hydrophobically with the corresponding helices of the other subunit to form a hydrophobic core at the center of the dimer. Two large pockets that exist between the first domain of one subunit and the second domain of the other include the amino acid residues responsible for substrate binding. These results indicate that the dimeric form is essential for the IPMDH to express enzymatic activity and that the close subunit contact at the hydrophobic core is important for the thermal stability of the enzyme.
Institute for Protein Research Osaka University, Japan.