Lactate dehydrogenase from the hyperthermophilic archaeon Methanococcus jannaschii: overexpression, crystallization and preliminary X-ray analysis

L(+)-Lactate dehydrogenase (LDH) is a key enzyme in anaerobic metabolism wh ich converts pyruvate to lactate. LDH from the hyperthermophilic archaebact erium Methanococcus jannaschii has been overexpressed in Escherichia coli a nd crystallized in two crystal forms at 297 K using 2-methyl-2,4-pentanedio l as precipitant. Type I crystals grew rapidly and diffracted to at least 2 .8 Angstrom Bragg spacing upon exposure to Cu K alpha X-rays. X-ray diffrac tion data to 2.9 Angstrom have been collected from a native crystal. The ty pe I crystal is tetragonal, belonging to the space group P4(2)2(1)2, with u nit-cell parameters a = b = 99.74, c = 170.00 Angstrom. The asymmetric unit contains two LDH subunits, with a corresponding crystal volume per protein mass (V-m) of 3.05 Angstrom(3) Da(-1) and a solvent content of 59.7%. Type II crystals, which grew more slowly, diffracted to at least 1.8 Angstrom B ragg spacing upon exposure to Cu K alpha X-rays. X-ray diffraction data to 1.9 Angstrom have been collected from a native crystal. The type II crystal is orthorhombic, belonging to the space group P2(1)2(1)2, with unit-cell p arameters a = 47.65, b = 125.10, c = 58.08 Angstrom. The asymmetric unit co ntains a single LDH subunit, with a corresponding crystal volume per protei n mass (V-m) of 2.50 Angstrom(3) Da(-1) and a solvent content of 50.8%. The refore, the type II crystal is more suitable for high-resolution structure determination than the type I crystal.