Crystal structures of 3-isopropylmalate dehydrogenases with mutations at the C-terminus: crystallographic analyses of structure-stability relationships.
Thermal stability of the Thermus thermophilus isopropylmalate dehydrogenase enzyme was substantially lost upon the deletion of three residues from the C-terminus. However, the stability was partly recovered by the addition of two, four and seven amino acid residues (called HD177, HD708 and HD711, respectively) to the C-terminal region of the truncated enzyme. Three structures of these mutant enzymes were determined by an X-ray diffraction method. All protein crystals belong to space group P2(1) and their structures were solved by a standard molecular replacement method where the original dimer structure of the A172L mutant was used as a search model. Thermal stability of these mutant enzymes is discussed based on the 3D structure with special attention to the width of the active-site groove and the minor groove, distortion of beta-sheet pillar structure and size of cavity in the domain-domain interface around the C-terminus. Our previous studies revealed that the thermal stability of isopropylmalate dehydrogenase increases when the active-site cleft is closed (the closed form). In the present study it is shown that the active-site cleft can be regulated by open-close movement of the minor groove located at the opposite side to the active-site groove on the same subunit, through a paperclip-like motion.
Nurachman
Z
Z
Department of Life Science, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta 4259, Yokohama 226-8501, Japan.
Akanuma
S
S
Sato
T
T
Oshima
T
T
Tanaka
N
N
D050539:3-Isopropylmalate Dehydrogenase; D000429:Alcohol Oxidoreductases / Q000737:chemistry* / Q000235:genetics*; D001665:Binding Sites; D003460:Crystallization; D018360:Crystallography, X-Ray; D019281:Dimerization; D004795:Enzyme Stability; D006358:Hot Temperature; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D013329:Structure-Activity Relationship; D016963:Thermus thermophilus / Q000201:enzymology
D010446:Peptide Fragments; D000429:Alcohol Oxidoreductases; D050539:3-Isopropylmalate Dehydrogenase