CRYSTALLIZATION AND PRELIMINARY-X-RAY CRYSTALLOGRAPHIC ANALYSIS OF DNA-POLYMERASE FROM THERMUS-AQUATICUS

Two crystal forms of DNA polymerase from Thermus aquaticus have been g rown at room temperature. Rhombohedral crystals (form I) grown from am monium sulfate solution diffracted poorly to 10 Angstrom only and thus are not suitable for X-ray structure determination. Trigonal crystals (form II) grown from polyethylene glycol solution are more suitable f or structure determination since their diffraction pattern extends to 2.5 A at cryogenic temperature upon exposure to synchrotron X-rays. Th ey belong to space group P3(1)21 (or its enantiomorph P3(2)21) and the ir unit-cell dimensions are a=106.7 and c=169.7 Angstrom for flash-fro zen crystals. The presence of one molecule per asymmetric unit gives a crystal volume per protein mass (V-M) of 3.0 Angstrom(3) Da(-1) and a solvent content of 58% by volume. X-ray data have been collected to 2 .7 Angstrom Bragg spacing from native crystals.