scholarly journals tRNA2Thr Complements Temperature Sensitivity Caused by Null Mutations in the htrB Gene in Escherichia coli

2003 ◽  
Vol 185 (5) ◽  
pp. 1726-1729 ◽  
Author(s):  
Yoshio Mohri ◽  
Simon Goto ◽  
Kenji Nakahigashi ◽  
Hachiro Inokuchi
Keyword(s):  
Escherichia Coli ◽  
Protein Synthesis ◽  
Temperature Sensitivity ◽  
Lipid A ◽  
Temperature Sensitive ◽  
Temperature Sensitive Mutants ◽  
Lipid A Biosynthesis ◽  
Two Temperature ◽  
Temperature Sensitive Phenotype

ABSTRACT According to the wobble rule, tRNA2Thr is nonessential for protein synthesis, because the codon (ACG) that is recognized by tRNA2Thr is also recognized by tRNA4Thr. In order to investigate the reason that this nonessential tRNA nevertheless exists in Escherichia coli, we attempted to isolate tRNA2Thr-requiring mutants. Using strain JM101F−, which lacks the gene for tRNA2Thr, we succeeded in isolating two temperature-sensitive mutants whose temperature sensitivity was complemented by introduction of the gene for tRNA2Thr. These mutants had a mutation in the htrB gene, whose product is an enzyme involved in lipid A biosynthesis. Although it is known that some null mutations in the htrB gene give a temperature-sensitive phenotype, our mutants exhibited tighter temperature sensitivity. We discuss a possible mechanism for the requirement for tRNA2Thr.

scholarly journals LOCALIZED MUTAGENESIS FOR THE ISOLATION OF TEMPERATURE-SENSITIVE MUTANTS OF ESCHERICHIA COLI AFFECTED IN PROTEIN SYNTHESIS

Genetics ◽  
1979 ◽  
Vol 91 (2) ◽  
pp. 215-227
Author(s):  
W Scott Champney
Keyword(s):  
Escherichia Coli ◽  
Protein Synthesis ◽  
Temperature Sensitive ◽  
Chromosomal Locus ◽  
Ribosomal Subunits ◽  
Prolonged Incubation ◽  
Temperature Sensitive Mutants ◽  
Inhibition Of Growth ◽  
Localized Mutagenesis

ABSTRACT Two variations of the method of localized mutagenesis were used to introduce mutations into the 72 min region of the Escherichia coli chromosome. Twenty temperature-sensitive mutants, with linkage to markers in this region, have been examined. Each strain showed an inhibition of growth in liquid medium at 44°, and 19 of the mutants lost viability upon prolonged incubation at this temperature. A reduction in the rate of in vivo RNA and protein synthesis was observed for each mutant at 44°, relative to a control strain. Eleven of the mutants were altered in growth sensitivity or resistance to one or more of three ribosomal antibiotics. The incomplete assembly of ribosomal subunits was detected in nine strains grown at 44°. The characteristics of these mutants suggest that many of them are altered in genes for translational or transcriptional components, consistent with the clustering of these genes at this chromosomal locus.

Genetic and biochemical studies of asparagine-linked oligosaccharide assembly

1982 ◽  
Vol 300 (1099) ◽  
pp. 207-223 ◽  
Keyword(s):  
Protein Synthesis ◽  
Temperature Sensitive ◽  
Temperature Sensitive Mutants ◽  
Isolation And Characterization ◽  
Oligosaccharide Processing ◽  
Biochemical Studies ◽  
The Common ◽  
Specific Lipid ◽  
Temperature Sensitive Phenotype

The formation of N -glycosidic linkages of eukaryotic glycoproteins involves the assembly of a specific lipid-linked precursor oligosaccharide in the endoplasmic reticulum. This oligosaccharide is transferred from the lipid carrier to appropriate asparagine residues during protein synthesis. The protein-linked oligosaccharide then undergoes processing reactions that include both removal and addition of carbohydrate residues. In this paper we report recent studies from our laboratory on the synthesis of asparagine-linked oligosaccharides. In the first part we describe the isolation and characterization of temperature-sensitive mutants of yeast blocked at specific stages in the assembly of the lipid-linked oligosaccharide. In addition, we are using these mutants to clone the genes for the enzymes in this pathway by complementation of the temperature-sensitive phenotype. The second part deals with the topography of asparagine-linked oligosaccharide assembly. Our studies on the transmembrane movement of sugar residues during the assembly of secreted glycoproteins from cytoplasmic precursors are presented. Finally, experiments on the control of protein-linked oligosaccharide processing are described. Recent data are presented on the problem of how specific oligosaccharides are assembled from the common precursors at individual sites on glycoproteins.

Protein synthesis kinetics with ribosomes from temperature-sensitive mutants of Escherichia coli

Biochemistry ◽  
1979 ◽  
Vol 18 (24) ◽  
pp. 5482-5489 ◽  
Author(s):  
Hamid Rahi ◽  
Cheryle P. Mothershed ◽  
W. Scott Champney
Keyword(s):  
Escherichia Coli ◽  
Protein Synthesis ◽  
Temperature Sensitive ◽  
Temperature Sensitive Mutants

scholarly journals Temperature-sensitive mutants ofPhysarum polycephalum– expression of mutations in amoebae and plasmodia

1979 ◽  
Vol 34 (1) ◽  
pp. 33-40 ◽  
Author(s):  
Tim Burland ◽  
Jennifer Dee
Keyword(s):  
Temperature Sensitivity ◽  
Growth Temperature ◽  
Physarum Polycephalum ◽  
Temperature Sensitive ◽  
Optimum Growth ◽  
Efficient Procedure ◽  
Temperature Sensitive Mutants ◽  
Temperature Sensitive Phenotype ◽  
Laborious Method

SUMMARYOver 100 temperature-sensitive mutants ofmt-h (apogamic) strains ofPhysarum polycephalumwere isolated either by testing clones of mutagenized amoebae (ATS mutants) or by the more laborious method of testing plasmodia derived from such clones (PTS mutants). When amoebae and plasmodia of each mutant were tested for growth temperature sensitivity on different media (to give optimum growth of each phase), only 21% of 73 ATS mutants and 32% of 31 PTS mutants appeared to be temperature-sensitive in both phases, suggesting that the majority of mutants are phase-specific, as concluded from several similar studies by previous authors. When the mutants were tested on a third medium which allows growth of both amoebae and plasmodia, many of the mutants no longer had a temperature-sensitive phenotype in either phase. Among the remainder, 51% of ATS mutants and 67% of PTS mutants were temperature-sensitive in both phases. It was suggested that certain media have a remedial effect on some temperature-sensitive mutants so that the phenotype is apparently normal. Thus, the proportion of phase-specific mutants may be over-estimated if tests of temperature-sensitivity are done on the different media commonly used for culture of amoebae and plasmodia respectively. It was concluded that the most efficient procedure for isolation of temperature-sensitive mutants expressed in plasmodia is to screen clones of amoebae on a medium resembling as closely as possible that which is to be used for testing plasmodia.

scholarly journals Lethal Action of Quinolones against a Temperature-Sensitive dnaB Replication Mutant of Escherichia coli

2006 ◽  
Vol 50 (1) ◽  
pp. 362-364 ◽  
Author(s):  
Xilin Zhao ◽  
Muhammad Malik ◽  
Nymph Chan ◽  
Alex Drlica-Wagner ◽  
Jian-Ying Wang ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Protein Synthesis ◽  
Dna Replication ◽  
Nalidixic Acid ◽  
Temperature Sensitive ◽  
Wild Type ◽  
Lethal Action ◽  
Inhibition Of Protein Synthesis

ABSTRACT Inhibition of DNA replication in an Escherichia coli dnaB-22 mutant failed to block quinolone-mediated lethality. Inhibition of protein synthesis by chloramphenicol inhibited nalidixic acid lethality and, to a lesser extent, ciprofloxacin lethality in both dnaB-22 and wild-type cells. Thus, major features of quinolone-mediated lethality do not depend on ongoing replication.

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