Abstract
Nuclei of Acanthamoeba castellanii were rapidly isolated and purified by discontinuous density gradients with a 80% overall yield. The nuclei showed morphological and physiological integrity as judged by the electron micrographs and the activity of RNA polymerase (EC 2.7.7.6). The average DNA, RNA and protein content of isolated amoeba nuclei was, respectively, 10.6, 2.1 and 38.8 pg per nucleus. A method was described which permits the recovery of a good yield of high-molecular-weight DNA from purified nuclei. The nuclear DNA is made of only one species banding at a density of 1.717 g/cm 3 which corresponds to a mean base composition of 58% G + C . This means that the major component obtained by density centrifugation of whole-cell DNA is solely of nuclear origin. The renaturation kinetics of nuclear DNA indicates the absence of a highly repetitive DNA fraction. The calculated kinetic complexity for the nuclear DNA was 1.42 · 10 11 daltons.
Published Version
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