Thermosensitive mutants of Escherichia coli unable to propagate RNA phage at 42 degrees C and altered in protein synthesis

Conditional mutations in the translational apparatus of Bacillus subtils

Four temperature sensitive mutants of B. subtilis were isolated by localized mutagenesis in the major ribosomal gene cluster, and charcterized genetically and biochemically. Three are mutations which cause temperature sensitivity in the elongation factor Ef-G, and one which has a similar effect on the elongation factor Ef-Tu. They map in a cluster near strA, with the temperature sensitive mutations in Ef-G mapping between the strA gene and the temperature sensitive mutation in Ef-TU.

Thermosensitive mutants of Escherichia coli K-12 altered in the catalytic Subunit and in a Regulatory factor of the glutamy-transfer ribonucleic acid synthetase

The glutamyl-transfer ribonucleic acid synthetase (GluRS) of a partial revertants (ts plus or minus) of the thermosensitive (ts) mutant strain JP1449 (LOcus gltx) and of a ts mutant strain EM111-ts1 with a lesion in or near the locus gltx have been studied to find the relation between these two genetic loci known to influence the GluRS activity in vitro and the presence of a catalytic subunit and of a regulatory subunit in the GluRS purified from Escherichia coli K-12. The ts character of strain JP1449-18ts plus or minus is co-transduced with the marker dsdA at the same frequency as is the ts character of strain JP1449. Its purified GluRS is very thermolabile and its Km for glutamate is higher than that of a wild-type GluRS. These results indicate that the locus gltX is in the structural gene for the catalytic subunit of this enzyme. The location of the mutation causing the partial ts reversion in strain JP1449-18ts plus or minus is discussed. The GluRS purified from the ts mutant strain EM111-ts1 has the same stability as the wild-type enzyme, but its Km forglutamate increases with the temperature, suggesting that the locus gltE codes for a regulatory factor, possibly for the polypeptide chain that is co-purified with the catalytic subunit.

Isolation and partial characterization of a temperature-sensitive Escherichia coli mutant with altered glutaminyl-transfer ribonucleic acid synthetase

A temperature-sensitive mutant of Escherichia coli has been found in which the conditional growth is a result of a thermosensitive glutaminyl-transfer ribonucleic acid synthetase. The corresponding genetic locus glnS is cotransduced with lip. In a strain containing the mutationally altered glutaminyl-transfer ribonucleic acid synthetase, no derepression of the enzyme itself nor of glutamine synthetase was observed.