bacterial lactate dehydrogenase
Biochemistry and Biotechnology
Wiley InterScience Backfile Collection 1832-2000
Bacillus stearothermophilus lactate dehydrogenase, one of the most thermostable bacterial enzymes known, has had its three-dimensional structure solved, the gene coding for it has been cloned, and the proteincan be readily overexpressed. Two mutants of the enzyme have been prepared. In one, Arg171 was changed to Trp (R171W) and Gln102 was changed to Arg (Q102R). In the other, the mutation Q102R was maintained, but Arg171 was changed to Tyr (R171Y). In addition, an inadvertent C97G mutant was present. Both mutants have been crystallized by the hanging drop vapor diffusion method at room temperature. Bipyrimidal crystals have been obtained against (NH4)2SO4in 50 mM piperazine HCI buffer. The crystals belong to space group P6622 (P6622) (whereas the native enzyme, the structure of which has been solved by Piontek et al., Proteins 7:74-92, 1990) crystallized in the space group (P61) with a = 102.3 Å, c = 168.6 Å for the R171W, Q102R, C97G triple mutant, and a = 98.2 Å; c = 162.1 Å for the R171Y, Q102R, C97G mutant. These crystal forms appear to contain one-quarter of a tetramer (Mr 135,000)in the asymmetric unit and have (VM values of 3.8 and 3.3 Å3/dalton, respectively). The R171W mutant diffracts to 2.5 Å and the R171Y mutant to approximately 3.5 Å © 1992 Wiley-Liss, Inc.
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