Effect of methyl methanesulphonate on the nucleoid structure of Escherichia coli

Journal of General Microbiology
I LossiusK Kleppe

Abstract

Incubation of a strain of Escherichia coli K12 with 25 mM-methyl methanesulphonate (MMS) for 1 h changed the sedimentation coefficient of the nucleoids from 1600S to 850S. When isolated nucleoids were treated with MMS under identical conditions in vitro there was no change in the sedimentation coefficient. Alkaline sucrose-gradient centrifugation of DNA from cells treated with 25 mM-MMS for 1 h indicated that there were approximately 100 breaks plus apurinic sites per chromosome. Titration with ethidium bromide of nucleoids from MMS-treated cells showed that almost all supercoiling had been lost, suggesting that the breaks plus apurinic sites consisted mostly of breaks. Further experiments showed that the apurinic sites were probably created by non-enzymic depurination and that little non-enzymic strand breakage had occurred. The depurinated sites thus created could then serve as substrates for the apurinic-specific endonucleases of the cell, with the result that strand breakage occurred. MMS treatment did not cause any changes in the DNA:RNA ratio of the nucleoids. Removal of MMS followed by a period of incubation resulted in a decrease in the number of breaks plus apurinic sites and an increase in the sedimentation coefficien...Continue Reading

Citations

Apr 1, 1983·Mutation Research·I LossiusK Kleppe
Jan 20, 1983·Biochimica Et Biophysica Acta·K SjåstadK Kleppe
May 1, 2013·Proceedings of the National Academy of Sciences of the United States of America·Stephan UphoffAchillefs N Kapanidis
Mar 1, 1984·Proceedings of the National Academy of Sciences of the United States of America·J H Krueger, G C Walker

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