1CM7: 3-isopropylmalate Dehydrogenase From Escherichia Coli

The basis of protein stability has been investigated by the structural comparison of themophilic enzymes with their mesophilic counterparts. A number of characteristics have been found that can contribute to the stabilization of thermophilic proteins, but no one is uniquely capable of imparting thermostability. The crystal structure of 3-isopropylmalate dehydrogenase (IPMDH) from the mesophiles Escherichia coli and Salmonella typhimurium have been determined by the method of molecular replacement using the known structure of the homologous Thermus thermophilus enzyme. The structure of the E. coli enzyme was refined at a resolution of 2.1 A to an R-factor of 17.3%, that of the S. typhimurium enzyme at 1.7 A resolution to an R-factor of 19.8%. The three structures were compared to elucidate the basis of the higher thermostability of the T. thermophilus enzyme. A mutant that created a cavity in the hydrophobic core of the thermophilic enzyme was designed to investigate the importance of packing density for thermostability. The structure of this mutant was analyzed. The main stabilizing features in the thermophilic enzyme are an increased number of salt bridges, additional hydrogen bonds, a proportionately larger and more hydrophobic subunit interface, shortened N and C termini and a larger number of proline residues. The mutation in the hydrophobic core of T. thermophilus IPMDH resulted in a cavity of 32 A3, but no significant effect on the activity and thermostability of the mutant was observed.
PDB ID: 1CM7Download
MMDB ID: 10512
PDB Deposition Date: 1999/5/17
Updated in MMDB: 2017/10
Experimental Method:
x-ray diffraction
Resolution: 2.06  Å
Source Organism:
Similar Structures:
Biological Unit for 1CM7: dimeric; determined by author and by software (PISA)
Molecular Components in 1CM7
Label Count Molecule
Proteins (2 molecules)
Protein (3-isopropylmalate Dehydrogenase)(Gene symbol: leuB)
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB