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A Tzagoloff

Publications and source records attributed to A Tzagoloff.

At least 127 records · Page 7Linked to original sources
PubMed1979

Assembly of the mitochondrial membrane system: partial sequence of a mitochondrial ATPase gene in Saccharomyces cerevisiae.

The nucleotide sequence of mitochondrial DNA of a cytoplasmic "petite" mutant of Saccharomyces cerevisiae is reported. The DNA has a repeat length of 1060 base pairs and contains a genetic marker (oli-1) for the ATPase proteolipid. The nucleotide sequence reveals the presence of part of the structural gene of the subunit-9 proteolipid of the ATPase complex and an extended A+T-rich region adjacent to the carboxyl-terminal end of the gene. The structural gene sequence agrees with the primary structure of the protein. These studies point out the feasibility of using the DNA of appropriately marked "petite" mutants to obtain the sequence of mitochondrial genes.

Adenosine Triphosphatases↗
PubMed1978

Assembly of the mitochondrial membrane system: mutations in the pho2 locus of the mitochondrial genome of Saccharomyces cerevisiae.

Two mutants of Saccharomyces cerevisiae which show a loss of mitochondrial rutamycin-sensitive ATPase activity are described. Although phenotypically similar to mutants of the mitochondrial locus pho1 [F. Foury and A. Tzagoloff (1976) Eur. J. Biochem. 68, 113-119], these mutants define a second ATPase locus on the mitochondrial DNA (designated pho2), which is genetically unlinked to pho1. Analysis of recombination in crosses involving multiple antibiotic resistance markers indicates that the locus is in the segment of the genome between ery1 and oli2, very close to oli1. In fact it is proposed that the oli1 and pho2 mutations are in the same gene. Supporting evidence for this proposal includes: 1. The analysis of marker retention in petite mutants shows that the oli1 and pho2 loci were either retained or lost together in all cases. 2. Recombination frequencies of 0.05% or less are observed in crosses between the oli1 and pho2 loci. 3. When rho+ revertants are isolated from the pho2 mutants they frequently are oligomycin resistant. 4. pho2 mutants have an altered subunit 9 of the ATPase complex.

Adenosine Triphosphatases↗
PubMed1978

Assembly of the mitochondrial membrane system. Genetic complementation of mit- mutations in mitochondrial DNA of Saccharomyces cerevisiae.

A method has been devised to test intergenic complementation of mutations in the mitochondrial DNA of Saccharomyces cerevisiae. The test is based on the observation that diploids issued from pairwise crosses of certain mit- mutants with deficiencies in cytochrome oxidase, or coenzyme QH2-cytochrome c reductase, acquire high levels of respiratory activity shortly after zygote formation. Under our experimental conditions neither biochemical complementation, interallelic complementation, nor recombination has been found to contribute to any significant extent toward the respiration measured in the diploids at early times. The test has been used to study the number of complementation groups represented by a large number of mit- mutants. Results of pairwise crosses of mutants in the oxi 1, oxi 2, oxi 3, cob 1, and cob 2 loci indicate that complementation occurs between the oxi and cob loci between different oxi loci but not between the two cob loci. The five loci have, therefore, been assigned to four different complementation groups.

DNA, Mitochondrial↗
PubMed1976

Assembly of the mitochondrial membrane system. XVIII. Genetic loci on mitochondrial DNA involved in cytochrome b biosynthesis.

1. Fourteen cytoplasmic mutants of Saccharomyces cerevisiae with a specific deficiency of cytochrome b have been studied. The mutations have been shown to occur in two separate genetic loci, COB 1 and COB 2. These loci can be distinguished by mit- X mit- crosses. Pairwise crosses of cytochrome b mutants belonging to different loci yield 4-6% wild type recombinants corresponding to recombinational frequencies of 8-12%. In intra-locus crosses, the recombinational frequencies range from 1% to less than 0.01%. The two loci can also be distinguished by mit- X rho- crosses. Twenty rho- testers have been isolated of which ten preferentially restore mutations in COB 1 and ten others in COB 2. 2. The COB 1 and COB 2 loci have been localized on mitochondrial DNA between the two antibiotic resistance loci OLI 1 and OLI 2 in the order OLI 2-COB 2-COB 1-OLI 1. The results of mit- X mit- and mit- X rho- crosses have also been used to map the cytochrome b mutations relative to each other. The maps obtained by the two independent methods are in good agreement. 3. Mutations in COB 1 have been found to be linked to the OLI1 locus in some but not in other strains of S. cervisiae. This evidence suggests that there may be a spacer region between the two loci whose length varies from strain to strain. 4. Two mutations in COB 2 have been found to cause a loss of a mitochondrial translation product corresponding to the cytochrome b apoprotein. Instead of the wild type protein the mutants have a new low-molecular weight product which is probably a fragment of cytochrome b. The fact that the mutations revert suggests that they are nonsense mutations in the structural gene of cytochrome b.

Anti-Bacterial Agents↗
PubMed1976

Localization in yeast mitochondrial DNA of mutations expressed in a deficiency of cytochrome oxidase and/or coenzyme QH2-cytochrome c reductase.

1. Three methods are described for the genetic analysis of yeast cytoplasmic mutants (mit- mutants) lacking cytochrome oxidase or coenzyme QH2-cytochrome c reductase. The procedures permit mutations in mitochondrial DNA to be mapped relative to each other and with respect to drug-resistant markers. The first method is based upon the finding that crosses of mit- mutants with some but not other isonuclear q- mutants lead to the restoration of respiratory functions. Thus a segment of mitochondrial DNA corresponding to a given mit- mutation or to a set of mutations can be delineated. The second method is based on the appearance of wild-type progeny in mit- X mit- crosses. The third one is based on the analysis of various recombinant classes issued from crosses between mit-, drug-sensitive and mit+, drug-resistant mutants. Representative genetic markers of the RIBI, OLII, OLI2 and PAR1 loci were used for this purpose. 2. The three methods when applied to the study of 48 mit- mutants gave coherent results. At least three distinct regions on mitochondrial DNA in which mutations cause loss of functional cytochrome oxidase have been established. A fourth region represented by closely clustered mutants lacking coenzyme QH2-cytochrome c reductase and spectrally detectable cytochrome b has also been studied. 3. The three genetic regions of cytochrome oxidase and the cytochrome b region were localized by the third method on the circular map, in spans of mitochondrial DNA defined by the drug-resistant markers. The results obtained by this method were confirmed by analysis of the crosses between selected mit- mutants and a large number of q- clones whose retained segments of mitochondrial DNA contained various combinations of drug-resistant markers. 4. All the genetic data indicate that the various regions studied are dispersed on the mitochondrial genome and in some instances regions or clusters of closely linked mutations involved in the same respiratory function (cytochrome oxidase) are separated by other regions which code for entirely different functions such as ribosomal RNA.

Chromosome Mapping↗
PubMed1976

Localization on mitochondrial DNA of mutations leading to a loss of rutamycin-sensitive adenosine triphosphatase.

Four cytoplasmic mutants of Saccharomyces cerevisiae showing loss of mitochondrial rutamycin-sensitive ATPase activity but having significant cytochrome oxidase and NADH-cytochrome c reductase have been isolated. Genetic studies indicate the mutations to be closely linked to each other and have been assigned to a new locus, PHO1. The mutations show a low frequency of recombination with the OL12 locus, suggesting a linkage to this marker. They are not, however, linked to the OLI1 locus. Linkage of the ATPase mutations to the OLI2 locus is also indicated by restoration of wild-type diploids by sigma- clones that retain the segment of mitochondrial DNA carrying OLI2. Based on the recombinants issued from crosses of the mutants with a triple drug-resistant strain and an analysis of the resistance markers present in sigma- clones that are effective in restoring a wild-type phenotype, the PHO1 locus has been placed in the segment of DNA located between PAR1 and OLI2.

Adenosine Triphosphatases↗
PubMed1975

Assembly of the mitochondrial membrane system. Characterization of nuclear mutants of Saccharomyces cerevisiae with defects in mitochondrial ATPase and respiratory enzymes.

Mutants of Saccharomyces cereviaiae showing defects in cytochrome oxidase, coenzyme QH2-cytochrome c reductase, and rutamycin-sensitive ATPase are described. The mutations have been established to be nuclear, based on complementation with a cytoplasmic petite tester strain and 2:2 segregation of tetrads. Genetic analysis indicate the coenzyme QH2-cytochrome c reductase and cytochrome oxidase mutants fall into 9 and 10 different complementation groups, respectively. The mutants also form distinct classes based on absorption spectra of the mitochondrial cytochromes. Two of the ATPase mutants lack detectable F1 ATPase, while the third synthesizes F1 but does not integrate it into a membrane complex. The latter mutant is missing one of the mitochondrially synthesized subunits of the rutamycin-sensitive ATPase complex.

Adenosine Triphosphatases↗
PubMed1975

Assembly of the mitochondrial membrane system. Cytoplasmic mutants of Saccharomyces cerevisiae with lesions in enzymes of the respiratory chain and in the mitochondrial ATPase.

Mutants of Saccharomyces cervisiae with defects in enzymes of the electron transfer chain and in the rutamycin-sensitive ATPase have been isolated. Some of the mutants are specifically affected in either cytochrome oxidase, coenzyme QH2-cytochrome c reductase or ATPase. Other strains are deficient in both cytochrome oxidase and coenzyme QH2-cytochrome c reductase but still have rutamycin-sensitive ATPase. All the mutants reported in this study fail to be complemented by a rho0 tester derived from a respiratory competent strain. The meiotic spore progeny obtained by mating the mutants to a respiratory competent haploid yeast, when scored for growth on glycerol, show a non-Mendelian segregation of the phenotype. These two genetic tests indicate the mutations to be cytoplasmically inherited.

Adenosine Triphosphatases↗
PubMed1975

Properties of cytoplasmic mutants of Saccharomyces cerevisiae with specific lesions in cytochrome oxidase.

Two mutants with specific defects in cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase; EC 1.9.3.1) have been isolated from cultures of Saccharomyces cerevisiae exposed to the mutagens ethyl-methane sulfonate and Mn++. The mutations have been shown to be extranuclear by two criteria. The phenotype persists in diploids formed by a cross with a p-o strain of yeast of the opposite mating type. Tetrad analysis indicates a non-Mendelian segregation (4:0 and 0:4) of the mutations. Both mutants show a total absence of cytochrome oxidase activity and of spectral cytochromes a and as. One of the mutants has been shown to be missing a polypeptide synthesized by mitochondria. The migration of this protein on polyacrylamide gels corresponds to the highest-molecular-weight subunit of cytochrome oxidase.

Diploidy↗
PubMed1975

Assembly of the mitochondrial membrane system: isolation of nuclear and cytoplasmic mutants of Saccharomyces cerevisiae with specific defects in mitochondrial functions.

A selection procedure is described which permits a large number of Saccharomyces cerevisiae mutants to be screened for specific lesions in mitochondrial respiratory enzymes and the adenosine triphosphatase. The method has been used to isolate nuclear mutant strains with specific lesions in coenzyme QH2-cytochrome c reductase, cytochrome oxidase, and adenosine triphosphatase. In addition, two cytoplasmic mutants have been found whose primary defect is in cytochrome oxidase, and others have been found that show variable degrees of abnormalities in their mitochondrial translation products.

Adenosine Triphosphatases↗
PubMed1975

Proteins of bacteriophage phi6.

We investigated the protein composition of the lipid-containing bacteriophage phi 6. We also studied the synthesis of phage-specific proteins in the host bacterium Pseudomonas phaseolicola HB10Y. The virion was found to contain 10 proteins of the following molecular weights: P1, 93,000; P2, 88,000; P3, 84,000; P4, 36,800; P5, 24,000; P6, 21,000; P7, 19,900; P8, 10,500; P9, 8,700; and P10, less than 6,000. Proteins P3, P9, and P10 were completely extracted from the virion with 1% Triton X-100. Protein P6 was partially extracted. Proteins P8 and P9 were purified by column chromatography. The amino acid composition of P9 was determined and was found to lack methionine. Labeling of viral proteins with [35S]methionine in infected cells indicated that proteins P5, P9, P10, and P11 lacked methionine. Treatment of host cells with UV light before infection allowed the synthesis of P1, P2, P4, and P7; however, the extent of viral protein synthesis fell off exponentially with increasing delay time between irradiation and infection. Treatment of host cells with rifampin during infection allowed preferential synthesis of viral proteins, but the extent of synthesis also fell off exponentially with increasing delay time between the addition of rifampin and the addition of radioactive amino acids. All of the virion proteins were seen in gels prepared from rifampin-treated infected cells. In addition, two proteins, P11 and P12, were observed; their molecular weights were 25,200 and 20,100, respectively. Proteins P1, P2, P4, and P7 were synthesized early, whereas the rest began to increase at 45 min post-infection.

Amino Acids↗