Respiratory deficient

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... 

Two bursts in the production of acid-soluble PolyPs were shown to occur during the growth of some S. cerevisiae strains on a medium containing glucose and galactose under aerobic conditions (Solimene et al., 1980). The respiratory deficient mutant, however, had only one PolyP burst , which indicated that the accumulation of PolyP produced in the first burst depended on the active mitochondrial function (Solimene et al., 1980). 

Coxl7, an 8.1-kDa cysteine-rich protein, was the first copper chaperone to be identified. Saccharomyces cerevisiae harboring mutations in coxl 7 are respiratory deficient, a phenotype resulting from their inability to assemble a functional cytochrome c oxidase complex (Glerum et al., 1996a). coxl7 mutant yeast are, however, able to express all the subunits of the cytochrome c oxidase complex, indicating that the lesion must lie in a posttranslational step that is essential for assembly of the functional complex in the mitochondrial membrane. Unlike other cytochrome c... 

Harrod et al. selected for respiratory deficient strains of P. tannophilus [158]. In P. tannophilus, utilization of malic and succinic acid is repressed by glucose. The authors characterized strains with mutations in two hexokinases and a glu-cokinase for their growth on glucose in the presence of L-malic and succinic... 

Many, perhaps most, chemical agents exert their lethal effects because of effects on the respiratory system and thus the provision of breathing support is essential. This is because toxic agents produce effects that cause blockage of the air passages, depression and failure of the respiratory control centres in the brain or paralysis of the muscles of respiration. To overcome these combined effects, the emergency medical response must include the ability to be able to clear and support the airway and also to be able to ventilate the lungs artificially when there is respiratory deficiency or arrest. This support is now part of a standard response for advanced life support in both conventional and toxic trauma and is termed TOXALS (Baker, 1996 Department of Health, 2003) (see Box 3). 

In the presence of [PS7+], nam9-l strains are respiratory-deficient, but in a psi background, nam9-l strains are respiratory-competent (Chacinska et al., 2000). While the molecular target of the read-through event(s) leading to this phenotype is not yet characterized, this observation provides an extremely useful tool for further [P.S7+] studies a positive selection for the [psi ] state. 

The existence of a mitochondrial pathway for de novo fatty acid synthesis was first reported 50 years ago, when it was generally assumed that fatty acid synthesis proceeded by reversal of the mitochondrial pathway for fatty acid P-oxidation (F. Lynen, 1957). However, the discovery of the cytosolic malonyl-CoA pathway (R.O. Brady, 1958 S.J Wakil, 1958) casted doubt on these claims and interest in this system waned until the discovery that mitochondria of both Neurospora crassa and Saccharomyces cerevisiae contain nuclear-encoded mitochondrial proteins that function as a type II FAS system. Disruption of the genes encoding these enzymes in both N. crassa and S. cerevisiae produces respiratory-deficient phenotypes and in S. cerevisiae cellular lipoic acid is reduced to less than 10% of that of the wild-type strain (R. Schneider, 1995 E. Schweizer, 1997). These observations suggested that in fungi one of the roles of this pathway might be to generate the lipoyl moieties required for mitochondrial function. 

Bernardi G., Faures M., Piperno G., Slonimski P.P. (1970). Mitochondrial DNA s from respiratory-sufficient and cytoplasmic respiratory-deficient mutant yeast. J. Mol. Biol. 48 23-42. 

The suitability of using the tRNA import pathway for the correction of respiratory deficiencies in the mitochondrial DNA and the applicability of this system for human therapeutic application were investigated. Mitochondrial import of nuclear encoded tRNAs has been described in yeasts, plants and protozoans. The complexity of the imported tRNA pool varies among organisms, from a complete set required for reading all codons of the mitochondrial genetic code in trypanosomatids to a single tRNA in the yeast S. cerevisiae. 

Clomethiazole has some respiratory depressant effeets, and is eontraindi-eated in patients with respiratory deficiency, but it is not clear why, having passed across the plaeenta into the foetus, its effeets should apparently be so markedly inereased by diazoxide. 

Damage to the respiratory chain is correlated with a decrease in ATP production and a lack of certain enzymes and cytochromes. These defects can be detected by measuring the autofluorescence of flavine molecules in intact and respiratory-deficient yeast strains with advanced microscopic techniques [1527a]. 

Respiratory-deficient mutant forms of brewing yeast arise from time to time. Because they produce a different balance of metabolic products than the parent strain, they tend to influence the flavour of the beer. For instance they may produce unacceptable levels of vicinal diketones, notably diacetyl. They arise spontaneously but may be induced by a variety of substances, including copper salts [97] and formaldehyde [98]. 

Respiratory-deficient cells are spontaneous mutants in which there is a deficiency in mitochondrial function (Stewart, 2014). 

The mitochondrial membranes also contain sterols, as well as numerous proteins and enzymes (Guerin, 1991). The two membranes, inner and outer, contain enzymes involved in the synthesis of phospholipids and sterols. The ability to synthesize signiflcant amounts of hpids, characteristic of yeast mitochondria, is not limited by respiratory deficient mutahons or catabohc glucose repression. 

Damage to the respiratory chain is correlated with a decrease in ATP production and a lack of certain enzymes and cytochromes. These defects can be detected by measuring the autofluorescence of flavin molecules in intact and respiratory deficient yeast strains with advanced microscopic techniques [15.114]. The combination of time-resolved laser spectroscopic techniques with a laser scanning microscope opens new possibilities for the investigation of dynamical processes with high spatial resolution. This is demonstrated in [15.114b] by time-resolved fluorescence measurements of carcinoma cells compared with normal cells. 

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