Molecular Pharmacology, Vol 4, 549-565, Copyright © 1968 by the American Society for Pharmacology and Experimental Therapeutics

Lethal Action and Metabolic Effects of Streptonigrin on Escherichia coli

¹ Department of Biochemistry, University of North Carolina, Chapel Hill, North Carolina 27514

Streptonigrin is lethal to cultures of Escherichia coli at concentrations that allow synthesis of DNA, RNA, and protein to continue. At higher concentrations DNA synthesis is preferentially inhibited. The lethal event is accompanied by DNA degradation, an effect enhanced if protein synthesis is also inhibited by witholding a required amino acid or by adding chloramphenicol. The degradation products, which are released into the culture medium, include nucleotides and bases, but no unusual products were detected. Both an electron source and oxygen are required for streptonigrin to exert its greatest lethal effect. This suggests that a reaction product of oxygen and intracellularly reduced streptonigrin is the lethal agent. This agent is likely to be a peroxide or peroxy free radical but is not hydrogen peroxide.

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ACKNOWLEDGMENT We thank T. O. Vaughan for technical assistance.