Crystallization and preliminary X-ray crystallographic analysis of DNA polymerase from Thermus aquaticus

Two crystal forms of DNA polymerase from Thermus aquaticus have been grown at room temperature. Rhombohedral crystals (form I) grown from ammonium sulfate solution diffracted poorly to 10 Å only and thus are not suitable for X-ray structure determination. Trigonal crystals (form II) grown from polyethylene glycol solution are more suitable for structure determination since their diffraction pattern extends to 2.5 Å at cryogenic temperature upon exposure to synchrotron X-rays. They belong to space group P3₁21 (or its enantiomorph P3₂21) and their unit-cell dimensions are a = 106.7 and c = 169.7 Å~, for flash-frozen crystals. The presence of one molecule per asymmetric unit gives a crystal volume per protein mass (V_M) of 3.0 Å³ Da^-l and a solvent content of 58% by volume. X-ray data have been collected to 2.7 Å Bragg spacing from native crystals.