Isolation of temperature-sensitive aminoacyl-tRNA synthetase mutants from an Escherichia coli strain harboring the pemK plasmid
1993
Masuda, Y. (Tokyo Univ. (Japan). Inst. of Applied Microbiology) | Tsuchimoto, S. | Nishimura, A. | Ohtsubo, E.
The pem locus, which is responsible for the stable maintenance of the low copy number plasmid R100, contains the pemK gene, whose product has been shown to be a growth inhibitor. Mutants were isolated which became tolerant to transient induction of the PemK protein. Nine of 20 mutants (here called pkt for PemK tolerance) were temperature sensitive for growth. The nine mutants were analysed genetically. They could be classified into three complementation groups, pktA, pktB and pktC, which corresponded to three genes, ileS, gltX and asnS, encoding isoleucyl- and glutamyl- and asparaginyl-tRNA synthetases, respectively. Since these amino- acyl-tRNA synthetase mutants did not produce the Pemk protein upon induction at the restrictive temperature, these mutants could be isolated because they behaved as if they were tolerant to the PemK protein. The procedure is therefore useful for isolating temperature-sensitive mutants of aminoacyl-tRNA synthetases.
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