Nucleic Acids Research, 1977, Vol. 4, No. 2 477-490
© 1977
Articles |
Physical properties of nucleoprotein cores from adenovirus type 5
Department of Biochemistry, School of Medicine, Case Western Reserve University Cleveland, OH 44106 USANational Institute for Medical Research Mill Hill, London NW7 1AA, UK
*Author to whom correspondence should be addressed.
Analytical ultracentrifugation, thermal denaturation, and electron microscopy have been used to study nucleoprotein core particles, obtained from disrupted type 5 adenovirus and partially purified on glycerol density gradients. Electron microscopy at low salt concentrations has shown that the cores are homogeneous particles with characteristic structures, which vary with conditions of observation from a fairly loose network of fibers to a highly condensed, compact particle. Sedimentation measurements in the analytical ultracentrifuge, both by boundary and by band techniques, show that the cores are relatively homogeneous in solution and have sedimentation coefficients near 185 S at low salt concentrations, about 243 S in 1 or 2 M NaCl, and 376 S in 1 mH MgCl2. Correlation of sedimentation data with electron microscopic observations suggests that the 185 S particle has a loose, fibrous structure, while the faster species are more highly condensed particles. The melting temperature of the cores in 5 mM Tris/ HCl is 79°C, which is 10°C higher than the Tm for purified, viral DNA. This indicates that the protein enhances the stability of DNA in the nucleoprotein complex.