Crystallization and Preliminary X-Ray Studies of a Bacillus subtilis and Thermus thermophilus HB8 Chimeric 3-Isopropylmalate Dehydrogenase and Thermostable Mutants of It

: A new type of chimeric 3-isopropylmalate dehydrogenase (2T2M6T) was produced by expressing the fused gene of Bacillus subtilis and Thermus thermophilus. The enzyme shows heat stability intermediate between those of the parents. The crystal of the enzyme belongs to the space group of P3(2)21, with cell dimensions of a = b = 78.9 A and c = 158.9 A. Two thermostable mutants of the chimeric enzyme were prepared by site-directed mutagenesis and then crystallized.