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Biomedical subjects

M Trucksis

Publications and source records attributed to M Trucksis.

20 records · Page 2Linked to original sources

Escherichia coli and Salmonella typhimurium supX genes specify deoxyribonucleic acid topoisomerase I.

Mutations of the Escherichia coli or Salmonella typhimurium supX genes eliminated deoxyribonucleic acid topoisomerase I. Suppression of a supX amber mutation partially restored the topoisomerase. Multicopy plasmids carrying supX+ caused overproduction of topoisomerase. Thus, these supX genes were identified as topA genes which specify deoxyribonucleic acid topoisomerase I.

DNA Topoisomerases, Type I↗

Salmonella typhimurium mutants with reduced levels of transfer ribonucleic acid-inhibitable endodeoxyribonucleolytic activity.

Two methods of mutagenesis, chemical alkylation and insertion of the tetracycline resistance transposon Tn10, were used to generate mutants of Salmonella typhimurium which had reduced levels of endodeoxyribonucleolytic activity. The chemically induced mutations defined a locus, endA, which was cotransduced with serA at a low frequency and with metK at a high frequency. Three-factor crosses revealed that metK was between serA and endA. The major endodeoxyribonucleolytic activity in crude extracts of s. typhimurium was similar to the activity of Escherichia coli endonuclease I. A Tn10 insertion mutation of endA resulted in the most severe loss of endodeoxyribonucleolytic activity among the endA alleles studied. Two of the chemically induced mutations resulted in activities which were more thermolabile than the wild-type activity.

DNA Transposable Elements↗