Effect of Metal Ions on Transcription of the ada Gene Which Encodes O⁶-Methylguanine-DNA Methyltransferase of Escherichia coli

Abstract

The effect of metal ions on transcription of the ada gene of Escherichia coli which is promoted by Ada protein in the presence of methylated deoxyribonucleic acid (DNA) was examined in a reconstituted system. Their effect on the O⁶-methylguanine-DNA methyltransferase (MGTase) activity of Ada protein was also examined. Ag⁺, Cd²⁺, Cu²⁺ and Hg²⁺ severely inhibited transcription of the ada gene at a dose which inhibited neither transcription of the lacUV5 gene nor MGTase activity. Zn²⁺ inhibited both transcription and MGTase activity in the same does range. Al³⁺ and Fe³⁺ inhibited transcription of both ada and lacUV5 genes without affecting the MGTase activity of Ada protein.