Respiratory deficient yeasts

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]. 

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. 

Wang, X., Gong, C.S., Tsao, G.T., 1988. Production of L-malic acid via biocataly-sis employing wild-type and respiratory-deficient yeast. Applied Biochemistry and Biotechnology 70-72,845-852. 

Chromosomal pleiotropic respiratory-deficient yeast mutants with multiple cytochrome deficiencies were first described by Sherman and SlonimskP in S, cerevisiae. Several combinations of cytochromes aa, b, c, and Cl deficiencies have been described more recently. The most common pleiotropic cytochrome deficiencies in S. cerevisiae concern both cytochromes aaz and b (strains pi, p6, p7 of ref. 85, strain plO of ref. 91, and strains S5, S6, S7, S9, S13, S19, and S20 of ref. 92). Strains 8, 16, 25, 486, 881, and El of ref. 93 might also be classified in the same class, although an additional deficiency in cytochrome Ci was reported. 

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... 

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... 

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. 

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]. 

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. 

S. cerevisiae is studied in regard to the biochemical regulation of malic acid production (Pines et al., 1996). Under environmentally stressed conditions, a small amoxmt of fumaric acid and malic acid (less than lOg/L) was produced by this common yeast. Similar to the malic acid production pathway of Aspergillus, the cytosolic reductive pathway of acid synthesis and accumulation has been shown in S. cerevisiae. A NMR study involving glucose conversions to malic acid indicates that the following reactions lead to malic acid accumulation pyruvate oxaloacetate->fumarate malate. The involvement of cytosolic fumarase in the conversion of fumaric acid to malic acid has been corroborated. Wang et al. (1988) have shown the ability of a cytoplasmic respiratory deficient mutant of S. cerevisiae to convert fumarate to malate without the participation of mitochondrial fumarase. 

Stable Pleiotropic Respiratory-Deficient Mutants of a Petite-Negative Yeast... 

When dealing with pleiotropic respiratory-deficient mutants of yeast, three practical difficulties constantly arise. The major inconvenience is the general genetic instability of the chromosomal pleiotropic respiratory-deficient mutants in S. cerevisiae where an additional p mutation spontaneously arises with very high frequency Since both the nuclear and the mitochondrial mutations are often expressed by deficient cytochromes aas and b, as well as by the loss of oligomycin sensitivity of the ATPase, the biochemical study of these double mutants is very difficult. An easy way out of this difficulty is to use chromosomal respiratory-deficient mutants of a petite-negative yeast species like 5. pombe, where no viable p mutation can be induced. 

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