The interaction of spermine and pentamines with DNA.

We studied the effects of spermine, two naturally-occurring pentamines isolated from the thermophile Thermus thermophilus and one synthetic pentamine on the aggregation and 'melting' temperature of calf-thymus DNA and on the B-to-Z transition of poly(dG-me5dC). All pentamines caused aggregation of DNA at much lower concentrations than that of spermine. Concentrations that increased the melting temperature of DNA and induced the B-to-Z transition in poly(dG-me5dC) were different for each pentamine, but were comparable with the concentration of spermine needed to cause these effects. Our results suggest that both the total charge and the distance separating the charge, which is a function of the length of the carbon chains between amino groups, are important for the induction of conformational changes in DNA. The biological role of pentamines in T. thermophilus appears to be related to their ability to promote DNA condensation at high temperature.