Conformation of the high molecular weight form ofDunaliella salina phosphofructokinase in solution by means of small-angle X-ray diffraction and viscosity measurements

The intrinsic viscosity of phosphofructokinase fromDunaliella salina in different states of aggregation was determined. The instrinsic viscosity [η], of the biologically active tetramer, with a molecular weight of 320,000, was found to be 6.5 ml·g−1 at 4°C. Moreover, for the inactive dimer, with a molecular weight of 160,000, a value of [η]=8.0 ml·g−1 was determined. The high molecular weight aggregate of phosphofructokinase fromDunaliella salina, that shows little activity, has an intrinsic viscosity of 23.2 ml·g−1, which is significantly higher than that found for the active tetramer and the inactive dimer.