STUDIES ON THE ANTIVIRAL ACTIVITY OF DISTAMYCIN A

Genetic and physiological studies on the site of action of distamycin A

Two new genetic loci of Bacillus subtilis are identified by mutations that confer resistance to distamycin A and to other antibacterial agents. The chromosomal region where they map probably contains a cluster of genes whose products are related to membrane structure and function. Some of the biological effects of distamycin A are still in evidence in the resistant mutants indicating that the drug possibly acts at multiple sites. Most biological effects of the drug (including the phenotypic correction of a morphopoietic mutation) are likely to be due to the interaction of distamycin A with membrane (or surface) structures.

Interaction between deoxyribonucliec acid and distamycin A studied by transformation in Bacillus subtilis

Distamycin A inhibits deoxyribonucleic acid (DNA)-mediated transformation and transfection in Bacillus subtilis at doses with little or no antibacterial effect. The inhibition of transformation parallels the inhibition of DNA uptake; further-more, during the transformation process, donor DNA molecules become distamycin and deoxyribonuclease resistant at the same time. This demonstrates that the drug acts by inhibiting DNA uptake. Although the drug is known to bind DNA, the inhibition is not related to affinity of the drug for DNA. This is shown by the lack of dependence of the extent of inhibition on DNA concentration, whereas the degree of inhibition depends upon cell concentration. Supporting this view is the fact that transformation by single-stranded DNA was also inhibited, even though the drug does not bind to denatured DNA. Distamycin A probably interferes with transformation by competing with DNA for some unknown bacterial component involved in transport of DNA into the cell.

Congocidine and distamycin A, antipoxvirus antibiotics

The antibiotics congocidine and distamycin A inhibited the replication of Shope fibroma and vaccinia viruses in BSC(1) cells. Treatment of infected cultures with congocidine for a 12-hr period resulted in an irreversible inhibitory effect on virus development. A longer period of treatment with the antibiotic also resulted in inhibition of the residual infectious virions present in the treated cells. Distamycin A inhibited the replication of poxviruses, but its inhibitory effect was reversed when the antibiotic was removed from the infected cells even as long as 24 hr after treatment. The inhibitory effect of distamycin A and its reversibility resembled the antipoxvirus activity of rifampin.

Effect of antiviral agents in equine abortion virus-infected hamsters

Equine abortion virus, a member of the herpesvirus group, produces a lethal infection in hamsters. With this system, the protective effect of certain inhibitors of deoxyribonucleic acid viruses, inducers of interferon and exogenous interferon, was evaluated. Of the various agents studied, 9-beta-d-arabinofuranosyladenine markedly suppressed mortality, and 5-iodo-2'-deoxyuridine, distamycin A, and N-ethylisatin beta-thiosemicarbazone were inactive. Of the inducers tested, statolon, ultraviolet-irradiated Newcastle disease virus, and polyriboinosinic:polyribocytidylic acid (poly I:C) were protective, and endotoxin, polyacrylic acid, and polymethacrylic acid did not protect. Administration of exogenous interferon did not afford protection. Statolon and ultraviolet-irradiated Newcastle disease virus induced circulating interferon in hamsters, whereas poly I:C, endotoxin, and polyacrylic acid did not produce interferon. Because of the severity of the disease produced in hamsters by equine abortion virus, lack of protective activity by an agent in this system should not preclude possible efficacy against other members of the herpesvirus group.

Optical rotatory dispersion properties of nucleic acid complexes with the oligopeptide antibiotics distamycin A and netropsin

ORD measurements of nucleic acids in the presence of the oligopeptides netropsin and distamycin A have indicated association of the antibiotics with DNA and strong conformational changes of the DNA structure with specificity to AT-rich helical regions. The RNA conformation is relatively unaffected by these antibiotics. The results are explained in terms of a perturbation of the DNA secondary structure as well as of the chromophore system of the oligopeptides.

Effect of distamycin a on the structure and template activity of DNA in RNA - polymerase system

It is shown that native and denatured DNA form complexes with the oligopeptide-antibiotic distamycin A. The pronounced inhibition of the incorporation of AMP into RNA in the DNA directed RNA-polymerase system is due to the interference of the antibiotic with DNA.