Mode of action of streptozotocin

Streptozotocin induces rapid degradation of deoxyribonucleic acid (DNA) in actively dividing or resting Bacillus subtilis cells. Difference spectroscopy showed that the antibiotic interacts specifically with cytosine containing mononucleotides in vitro. This interference occurs only within the very narrow pH range of 5 to 5.5 and is reversed immediately upon lowering or increasing the pH. No measurable interaction was observed between isolated DNA and streptozotocin. The possibility is discussed that interaction of streptozotocin with cytosine residues in cellular DNA, although possibly taking place at a very low frequency, may constitute the primary step inducing DNA strand breakage.