Preliminary crystallographic studies of an extremely thermostable KDG aldolase from Sulfolobus solfataricus

Crystals have been grown of 2-keto-3-deoxygluconate aldolase (KDG aldolase) from the hyperthermophilic archaeon Sulfolobus solfataricus that diffract to 2.2 Angstrom resolution. The enzyme catalyses the reversible aldol cleav age of 2-keto-3-dexoygluconate to pyruvate and glyceraldehyde, the third st ep of a modified non-phosphorylated Entner-Doudoroff pathway of glucose oxi dation. S. solfataricus grows optimally at 353 K and the enzyme itself has a half-life of 2.5 h at 373 K. Knowledge of the crystal structure of KDG al dolase will further understanding of the basis of protein hyperthermostabil ity and create a target for site-directed mutagenesis of active-site residu es, with the aim of altering substrate specificity. Three crystal forms hav e been obtained: orthorhombic crystals of space group P2(1)2(1)2(1), which diffract to beyond 2.15 Angstrom, monoclinic crystals of space group C2, wh ich diffract to 2.2 Angstrom, and cubic crystals of space group P4(2)32, wh ich diffract to 3.4 Angstrom.