Mutants temperature sensitive

Mutations Much of our knowledge of viral reproduction and how it is regulated has depended on the isolation and characterization of virus mutants. Several kinds of mutants have been studied in viruses host-range mutants, plaque-type mutants, temperature-sensitive mutants, nonsense mutants, transposons, and inversions. 

Yaffe MP, Ohta S, Schatz G (1985) A yeast mutant temperature-sensitive for mitochondrial assembly is deficient in a mitochondrial protease activity that cleaves imported precursor polypeptides. EMBO J 4 2069-2074... 

Mutation. For industrial appHcations, mutations are induced by x-rays, uv irradiation or chemicals (iiitrosoguanidine, EMS, MMS, etc). Mutant selections based on amino acid or nucleotide base analogue resistance or treatment with Nystatin or 2-deoxyglucose to select auxotrophs or temperature-sensitive mutations are easily carried out. Examples of useful mutants are strains of Candida membranefaciens, which produce L-threonine Hansenu/a anomala, which produces tryptophan or strains of Candida lipolytica that produce citric acid. An auxotrophic mutant of S. cerevisiae that requires leucine for growth has been produced for use in wine fermentations (see also Wine). This yeast produces only minimal quantities of isoamyl alcohol, a fusel oil fraction derived from leucine by the Ehrlich reaction (10,11). A mutant strain of bakers yeast with cold-sensitive metaboHsm shows increased stabiUty and has been marketed in Japan for use in doughs stored in the refrigerator (12). 

Palese P, Tobita K, Ueda M, Compans RW (1974b) Characterization of temperature sensitive influenza virus mutants defective in neuraminidase. Virology 61 397 10 Pegg MS, von Itzstein M (1994) Slow-binding inhibition of sialidase from influenza virus, Biochem Mol Biol Int 32 851-858... 

Using a random mutagenesis approach, respiratory-deficient (34) and temperature-sensitive (46, 47) mutants of the Rieske protein of the yeast bc complex have been selected. A large fraction of the point mutants had changes of residues in the bottom of the cluster binding subdomain (the loop /S7-/38) and in the Pro loop comprising residues 174-180 of the ISF (Fig. 9 see Section III,B,3) this indicates the importance of the Pro loop for the stability of the protein. Amino... 

Temperature-sensitive mutations are those which allow a virus to replicate at one temperature and not at another, due to a mutational alteration in a virus protein that renders the protein unstable at moderately high temperatures. For instance, temperature-sensitive mutants are known in which the phage will not be replicated in the host at 43 °C but will at 25 °C, although the host functions at both temperatures. Such mutations are called conditionally lethal, since the virus is unable to reproduce at the higher temperature, but replicates at the lower temperature. 

The importance of endocytosis for the normal function of the nerve terminal is demonstrated by the shibire mutant of Drosophila. When these mutant flies, bearing a temperature-sensitive allele, are exposed to high temperature,... 

A representative of a pentaacyl lipid A, in which the only secondary fatty acid present is associated with GlcN(I), is precursor lb (Fig. 9 B). This compound was isolated from a temperature-sensitive mutant of S. typhi-murium (mutant Ts5) (173). The only 3-acyloxyacyl residue in precursor lb is 14 O[3-0(16 O)], which is amide-linked to GlcN (I) (position 2). 

From these experiments it is not possible to find out whether the El protein has its separate signal peptide, mainly because of the low yields of the El protein in the synchronized translation experiments. However, evidence for such a peptide has come from studies with a temperature-sensitive mutant of SFV in which the cleavage between the capsid and the p62 protein is blocked (Hashimoto etal., 1981). In cells infected with this mutant at the restrictive temperature, the El protein is assembled in the correct orientation into the membrane of the ER. The uncleaved protein containing the capsid and the p62 sequences (Mr = 87,000) is left in the cytoplasm. These findings suggest that the El protein has its own signal peptide which might be located in the 6K protein. 

A successful tool in the early studies of metabolic pathways was blocking the pathway at some specific point. This could be done by the use of either mutants or inhibitors. Schekman et al have isolated a number of yeast mutants with blocks in their secretion pathway (Schekman, 1982). It is not yet known which proteins these mutations affect, but this is clearly a most promising approach for identifying those components involved in transport. In animal cells there are no cellular mutants with blocks in the intracellular transport of protein from the ER to the cell surface. There are, however, genetic diseases which affect the routing of lysosomal enzymes to the lysosomes (Neufeld et al, 1975 Sly and Fischer, 1982). For viruses it has been possible to isolate temperature-sensitive mutants in which a mutation in the viral glycoprotein arrests... 

Damke H, Baba T, van der Bliek AM, Schmid SL. Clathrin-independent pino-cytosis is induced in cells overexpressing a temperature-sensitive mutant of dynamin. J Cell Biol 1995 131(l) 69-80. 

Owen-Schaub LB, Zhang W, Cusack JC, etal. Wild-type human p53 and a temperature-sensitive mutant induce Fas/APO-1 expression. Mol Cell Biol 1995 15 3032-3040. 

In the presence of tunieamycin, cells infected with Rous sarcoma virus produced virus particles that lacked infectivity, and were devoid of the envelope glycoproteins gp85 and gp35. Virus particles lacking envelope glycoproteins had previously been found in a deletion mutant of Rous sarcoma virus and in a temperature-sensitive mutant of... 

Azarnia R, Loewenstein WR Intercellular communication and the control of growth. X. Alteration of junctional permeability by the sre gene. A study with temperature-sensitive mutant Rous sarcoma virus. J Membr Biol 1984 82 191-205. 

Palase P, Tobita K, Ueda M, Compans RW. Characterization of temperature sensitive influenza virus mutants defective in neuraminidase. Virology 1974 61 397-410. 

Is this a vital enzyme, one without which cells cannot grow and survive Again in E. coli, we have attempted to answer this question by isolation of temperature-sensitive mutants that will grow at a low (15°-... 

The third method uses genetic mutation as the primary tool. This method requires the isolation of conditional mutants, that is, mutants that behave normally under one set of conditions but abnormally under another. Most commonly, temperature-sensitive DNA replication mutants are used. Such mutants have been isolated in E. coli, and they grow normally at a low (permissive) temperature (33°C) but poorly or not at all at a high (nonpermissive) temperature (41°C). Preliminary analysis of the temperature-sensitive step provides clues to the stage of replication affected. For... 

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