4HHM

Crystal structure of a mutant, G219A, of Glucose Isomerase from Streptomyces sp. SK

Summary for 4HHM

• Entry DOI: 10.2210/pdb4hhm/pdb
• Related: 4HHL
• Descriptor: Xylose isomerase, COBALT (II) ION, MAGNESIUM ION, ... (4 entities in total)
• Functional Keywords: tim-barrel, isomerase
• Biological source: Streptomyces sp. SK
• Total number of polymer chains: 8
• Total formula weight: 344763.78

Authors

Ben Hlima, H.,Riguet, J.,Haser, R.,Aghajari, N. (deposition date: 2012-10-10, release date: 2013-03-27, Last modification date: 2023-09-20)

Primary citation

Ben Hlima, H.,Bejar, S.,Riguet, J.,Haser, R.,Aghajari, N.
Identification of critical residues for the activity and thermostability of Streptomyces sp. SK glucose isomerase.
Appl.Microbiol.Biotechnol., 97:9715-9726, 2013

PubMed Abstract: The role of residue 219 in the physicochemical properties of D-glucose isomerase from Streptomyces sp. SK strain (SKGI) was investigated by site-directed mutagenesis and structural studies. Mutants G219A, G219N, and G219F were generated and characterized. Comparative studies of their physicochemical properties with those of the wild-type enzyme highlighted that mutant G219A displayed increased specific activity and thermal stability compared to that of the wild-type enzyme, while for G219N and G219F, these properties were considerably decreased. A double mutant, SKGI F53L/G219A, displayed a higher optimal temperature and a higher catalytic efficiency than both the G219A mutant and the wild-type enzyme and showed a half-life time of about 150 min at 85 °C as compared to 50 min for wild-type SKGI. Crystal structures of SKGI wild-type and G219A enzymes were solved to 1.73 and 2.15 Å, respectively, and showed that the polypeptide chain folds into two structural domains. The larger domain consists of a (β/α)8 unit, and the smaller domain forms a loop of α helices. Detailed analyses of the three-dimensional structures highlighted minor but important changes in the active site region as compared to that of the wild-type enzyme leading to a displacement of both metal ions, and in particular that in site M2. The structural analyses moreover revealed how the substitution of G219 by an alanine plays a crucial role in improving the thermostability of the mutant enzyme.

PubMed: 23463249
DOI: 10.1007/s00253-013-4784-2

Experimental method

X-RAY DIFFRACTION (2.15 Å)