Crystallization of F₁ ATPase from Rat Liver Mitochondria

ATPase (F₁) is obtained from rat liver mitochondria and purified through the diethylaminoethyl (DEAE) step. Before crystallization, a sample of the purified enzyme is subjected to electrophoresis in polyacrylamide gels containing sodium dodecyl sulfate (SDS). The pattern of electrophoretic mobilities obtained is indistinguishable from those of previously purified preparations. For crystallization purposes, the purified enzyme is dissolved at room temperature in a buffer containing 200mM potassium phosphate and 5mM ATP, pH 7.5. The protein concentration used for the crystallization experiments is approximately 20 mg/ml. The crystals grow to their final size in about 2–3 weeks. They are removed from the capillaries by flushing with a few milliliters of the external buffer and stored in small vials at room temperature. The crystals are shaped like small cubes. However, many of them have one dimension smaller than the other two dimensions. The crystal face that defines this dimension is not perpendicular to the others. The faces of the largest crystals obtained are nearly square and approximately 0.6 mm per side. If one crystal is redissolved and subjected to electrophoresis in SDS-containing gels, the pattern obtained is very similar to that of the starting material.