A temperature-sensitive DNA adenine methyltransferase mutant of Salmonella typhimurium |
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Authors: | Rolando Brawer Facundo D Batista Oscar R Burrone Daniel O Sordelli M C Cerquetti |
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Institution: | (1) Centro de Estudios Farmacolígicos y Botánicos (CEFYBO-CONICET) and University of Buenos Aires, School of Medicine, Serrano 669, 1414 Buenos Aires, Argentina e-mail: cris@cefybo.edu.ar Tel. +54-1-857-1434; Fax +54-1-856-2751, AR |
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Abstract: | A temperature-sensitive mutant of Salmonella typhimurium was isolated earlier after transposon mutagenesis with Tn10d Tet. The mutant D220 grows well at 28 °C but has a lower growth rate and forms filaments at 37 °C. Transposon-flanking fragments
of mutant D220 DNA were cloned and sequenced. The transposon was inserted in the dam gene between positions 803 and 804 (assigned allele number: dam-231 : : Tn10d Tet) and resulted in a predicted ten-amino-acid-shorter Dam protein. The insertion created a stop codon that led to a truncated
Dam protein with a temperature-sensitive phenotype. The insertion dam-231 : : Tn10d Tet resulted in a dam“leaky” phenotype since methylated and unmethylated adenines in GATC sequences were present. In addition, the dam-231 : : Tn10d Tet insertion rendered dam mutants temperature-sensitive for growth depending upon the genetic background of the S. typhimurium strain. The wild-type dam gene of S. typhimurium exhibited 82% identity with the Escherichia coli dam gene. |
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Keywords: | Salmonella typhimurium dam Temperature-sensitive mutant Insertion mutant |
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