Physicochemical characteristics of the DNA of parvovirus Lu 3.

Abstract

Tissue culture harvests of parvovirus Lu III were found to contain four types of particles banding at densities of 1.44, 1.415, 1.35, and 1.31 g/ml during equilibrium centrifugation in CsCl. Particles found at 1.31 g/ml were devoid of DNA. The nucleic acid molecules contained in virions of the other three fractions were analyzed for their physicochemical parameters. Particles banding at 1.415 g/ml are consistent with the main fraction of infectious virions. A DNA could be extracted which on the basis of its sedimentation behaviour in CsCl was supposed to consist of both single- and double-stranded molecules. By means of electron microscopy, digestion with an exonuclease, and chromatography on BND-cellulose, however, the DNA was shown to be a linear, single-stranded molecule with a molecular weight of about 1.59 ×106 daltons. The buoyant density of the DNA proved to be 1.7254 g/ml in neutral CsCl. The DNA represents about 28 per cent of the total molecular weight of parvovirus Lu III which then can be calculated to 5.7×106 daltons. The small fraction of infectious particles banding at 1.44 g/ml contained a DNA with quite similar characteristics. The nucleic acid molecules isolated from particles found at 1.35 g/ml however, are short single-stranded molecules with a molecular weight of 2.3×105 daltons only. They banded at the same density as did the DNA of infectious virions and, therefore, are assumed to represent small pieces of viral DNA.