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A Tzagoloff

Publications and source records attributed to A Tzagoloff.

At least 109 records · Page 6Linked to original sources
PubMed1980

Assembly of the mitochondrial membrane system. Complete restriction map of the cytochrome b region of mitochondrial DNA in Saccharomyces cerevisiae D273-10B.

The cytoplasmic petite (rho-) mutant DS400/A12 has been obtained from the wild type strain of Saccharomyces cerevisiae D273-10B/A21. The DS400/A12 clone has a mitochondrial genome with a 7.6-kilobase pair, tandemly repeated segment of DNA. Genetic tests indicate that DS400/A12 contains all the cob1 and cob2 markers of the cytochrome b gene. The gene has been further dissected by mutagenesis of DS400/A12 and selection of secondary rho- clones with simpler genotypes. Restriction analysis of the mtDNAs of the rho- clones was used to construct the complete restriction map of the cytochrome b region and to map the mutations within narrowly defined physical limits. The cytochrome b mutants scatter over a maximal distance of 3.3 kilobase pairs. All the mutations assigned previously to the cob2 locus are found between 71.6 and 73.2 units. The cob1 mutations are located between 74.6 and 76.3 units. The estimated distance between the two loci is at least 1 kilobase pair.

Cytochrome b Group↗
PubMed1980

Assembly of the mitochondrial membrane system. DNA sequence and organization of the cytochrome b gene in Saccharomyces cerevisiae D273-10B.

The mitochondrial genomes of cytoplasmic "petite" (rho-) mutants of Saccharomyces cerevisiae have been used to sequence the cytochrome b gene. A continuous sequence of 6.2 kilobase pairs has been obtained from 71.4 to 80.2 units of the wild type map. This region contains all the cytochrome b mutations previously assigned to the cob1 and cob2 genetic loci. Analysis of the DNA sequence has revealed that in the strain D273-10B, the cytochrome b gene is composed of three exons. The longest exon (b1) codes for the first 252 to 253 amino acids from the NH2-terminal end of the protein. The next two exons (b2 and b3) code for 16 to 18 and 115 to 116 amino acids, respectively. The complete cytochrome b polypeptide chain consists of 385 amino acids. Based on the amino acid composition, the yeast protein has a molecular weight of 44,000. The three exon regions of the cytochrome b gene are separated by two introns. The intron between b1 and b2 is 1414 nucleotides long and contains a reading frame that is continuous with the reading frame of exon b1. This intron sequence is potentially capable of coding for another protein of 384 amino acid residues. The second intron is 733 nucleotides long. This sequence is rich in A + T and includes a G + C cluster that may be involved in processing of the cytochrome b messenger. The organization of the cytochrome b region in S. cerevisiae D273-10B is somewhat less complex than has been reported for other yeast strains i which exon b1 appears to be further fragmented into three smaller exons.

Amino Acid Sequence↗
PubMed1980

Assembly of the mitochondrial membrane system. Sequences of yeast mitochondrial tRNA genes.

Two cytoplasmic "petite" (rho-) clones of Saccharomyces cerevisiae have been selected for the retention of the aspartic acid tRNA gene. The two clones, designated DS200/A102 and DS200/A5, have tandemly repeated segments of mitochondrial DNA (mtDNA) with unit lengths of 1,000 and 6,400 base pairs, respectively. The DS200/A102 genome has a single tRNA gene with a 3'-CUG-5' anticodon capable of recognizing the 5'-GAC-3' and 5'-GAU-3' codons for aspartic acid. The mtDNA segment of DS200/A102 has been determined to represent the wild type sequence from 5.3 to 6.8 map units. The genome of DS200/A5 is more complex encompassing the region of wild type mtDNA from 3.5 to 12.7 units. A continuous sequence has been obtained from 3.5 to 8.6 units. In addition to the aspartic acid tRNA, this region codes for the tRNAUGCAla,tRNAUCUArg, tRNAACGArg, tRNAGCUSer,tRNAUCCGly and tRNAUUULys. The DNA sequence of the DS200/A5 genome has allowed us to deduce the secondary structures of the seven tRNAs and to assign precise map positions for their genes. All the tRNAs except tRNA GUCAsp exhibit most of the invariant features of prokaryotic and eukaryotic tRNAs. The aspartic acid tRNA has unusual D and T psi C loops. The structure of this tRNA is similar to the mitochondrial initiator tRNA of Neurospora crassa (Heckman, J.E., Hecker, L.I., Shwartzbach, S.D., Barnett, W.E., Baumstark, B., and RajBhandary, U.L. Cell 13, 83-95).

Base Composition↗
PubMed1980

Assembly of the mitochondrial membrane system. Sequence of the oxi 2 gene of yeast mitochondrial DNA.

The region of mitochondrial DNA (mtDNA) containing the oxi 2 locus has been sequenced in a rho- clone (DS40) derived from the respiratory competent strain D273-10B/A48 of Saccharomyces cerevisiae. The DS40 clone was established to have retained only genetic markers in the oxi 2 locus and to have a segment of mtDNA extending from 18.6 to 24.3 units of the wild type map. The mitochondrial genome of DS40 includes a sequence that has been tentatively identified as the structural gene of Subunit 3 of cytochrome oxidase. The coding sequence is 810 nucleotides long and generates a protein with a molecular weight of 30,340. The amino acid composition of the oxi 2 gene product deduced from the nucleotide sequence is in agreement with the composition of the purified Subunit 3 of yeast cytochrome oxidase. The orientation of the DS40 mtDNA segment relative to wild type mtDNA indicates that the oxi 2 gene is transcribed from the same DNA strand as the oxi 1 and several other mitochondrial genes.

Adenosine Triphosphatases↗
PubMed1980

Assembly of the mitochondrial membrane system: sequence analysis of a yeast mitochondrial ATPase gene containing the oli-2 and oli-4 loci.

The mitochondrial DNA (mtDNA) segments of several rho- mutants carrying the oli-2, oli-4 and pho-1 loci have been sequenced. The segments contain a common structural gene sequence that has been identified to include all three genetic markers. The gene codes for a protein with a molecular weight of 28,257. This new gene is located between 61.5 and 62.6 units on the wild-type map of Saccharomyces cerevisiae and is transcribed from the same DNA strand as most other yeast mitochondrial genes sequenced to date. The amino acid composition and sequence deduced from the DNA sequence indicate that the protein is very hydrophobic, with three long domains (greater than 30 residues) consisting of nonpolar amino acids. Based on its molecular weight, the gene product is tentatively proposed to be either subunit 3 or 6 of the oligomycin-sensitive ATPase.

Adenosine Triphosphatases↗
PubMed1980

Codon recognition rules in yeast mitochondria.

The mitochondrial genome of Saccharomyces cerevisiae codes for 24 tRNAs. The nucleotide sequences of the tRNA genes suggest a unique set of rules that govern the decoding of the mitochondrial genetic code. The four codons of unmixed fmilies are recognized by single tRNAs that always have a U in the wobble position of the anticodon. The codons of the mixed families are read by two different tRNAs. Codons terminating in a C or U are recognized by tRNAs with a G and codons terminating in a G or A are recognized by tRNAs with a U in the corresponding positions of the anticodons. There are two exceptions to these rules. In the AUN family for isoleucine and methionine, the isoleucine tRNA has a G and the methionine tRNA has a C in the wobble position. The tRNA for the arginine CGN family also has an A in the wobble position of the anticodon. It is of interest that the CGN codons have not been found in the mitochondrial genes sequenced to date. The simplified decoding system of yeast mitochondria allows all the codons to be recognized by only 24 tRNAs.

Anticodon↗
PubMed1980

Assembly of the mitochondrial membrane system: nuclear suppression of a cytochrome b mutation in yeast mitochondrial DNA.

In a previous study, a mitochondrial mutant expressing a specific enzymatic deficiency in co-enzyme QH2-cytochrome c reductase was described (TZAGO-LOFF, FOURY and AKAI 1976). Analysis of the mitochondrially translated proteins revealed the absence in the mutant of the mitochondrial product corresponding to cytochrome b and the presence of a new low molecular weight product. The premature chain-termination mutant was used to obtain suppressor mutants with wild-type properties. One such revertant strain was analyzed genetically and biochemically. The revertant was determined to have a second mutation in a nuclear gene that is capable of partially suppressing the original mitochondrial cytochrome b mutation. Genetic data indicate that the nuclear mutation is recessive and is probably in a gene coding for a protein involved in the mitochondrial translation machinery.

Cytochromes↗
PubMed1980

Assembly of the mitochondrial membrane system: isolation of mitochondrial transfer ribonucleic acid mutants and characterization of transfer ribonucleic acid genes of Saccharomyces cerevisiae.

A method is described for isolating cytoplasmic mutants of Saccharomyces cerevisiae with lesions in mitochondrial transfer ribonucleic acids (tRNA's). The mutants were selected for slow growth on glycerol and for restoration of wild-type growth by cytoplasmic "petite" testers that contain regions of mitochondrial deoxyribonucleic acid (DNA) with tRNA genes. The aminoacylated mitochondrial tRNA's of several presumptive tRNA mutants were analyzed by reverse-phase chromatography on RPC-5. Two mutant strains, G76-26 and G76-35, were determined to carry mutations in the cysteine and histidine tRNA genes, respectively. The cysteine tRNA mutant was used to isolate cytoplasmic petite mutants whose retained segments of mitochondrial DNA contain the cysteine tRNA gene. The segment of one such mutant (DS504) was sequenced and shown to have the cysteine, histidine, and threonine tRNA genes. The structures of the three mitochondrial tRNA's were deduced from the DNA sequence.

Base Sequence↗
PubMed1979

Assembly of the mitochondrial membrane system. DNA sequence of subunit 2 of yeast cytochrome oxidase.

A cytoplasmic "petitie" mutant of Saccharomyces cerevisiae (DS200/A1) has been isolated and determined to contain mitochondrial genetic markers in the oxi 1 locus. This locus has previously been reported to code for the structural gene of subunit 2 of cytochrome oxidase (Cabral et al. (1978) J. Biol. Chem. 243, 297-304). The segment of mitochondrial DNA retained in DS200/A1 has a repeat length of approximately 4500 base pairs and based on DNA sequencing contains a 756-nucleotide-long sequence that has been identified as the structural gene of subunit 2 of cytochrome oxidase. The presumptive gene sequence generates an amino acid sequence consistent with the reported molecular weight and composition of subunit 2 of yeast cytochrome oxidase. The correctness of the deduced amino acid sequence is further supported by its extensive homology to the primary structure of bovine cytochrome oxidase. The DNA segment of DS200/A1 has been located on the wild type mitochondrial DNA by comparative restriction mapping. The orientation of the COOH and NH2 termini and the direction of transcription of the gene have been determined.

Amino Acid Sequence↗
PubMed1979

Assembly of the mitochondrial membrane system. The DNA sequence of a mitochondrial ATPase gene in Saccharomyces cerevisiae.

The mitochondrial DNA of a cytoplasmic "petite" mutant (DS400/A3) of Saccharomyces cerevisiae has been characterized by restriction endonuclease analysis and by DNA sequencing. The DNA has a repeat length of 1,800 base pairs and contains the oli 1 and pho 2 loci, two known markers of the ATPase proteolipid subunit. The nucleotide sequence has helped to establish the presence in the DS400/A3 DNA of the proteolipid gene flanked by two long stretches of DNA rich in A + T. The sequence of the structural gene is in excellent agreement with the previously reported primary structure of the proteolipid. The DNA sequence also indicates that the mitochondrial codons of yeast are highly nondegenerate. The proteolipid gene has been precisely localized on the restriction map of the wild type genome. In addition, it has been possible to orient the gene with respect to other genetic markers and to determine the direction of its transcription.

Adenosine Triphosphatases↗
PubMed1979

Assembly of the mitochondrial membrane system: two separate genes coding for threonyl-tRNA in the mitochondrial DNA of Saccharomyces cerevisiae.

1. Mitochondria of Saccharomyces cerevisiae contain two tRNA's that are acylated with threonine. The two isoaccepting species (tRNA1Thr and tRNA2Thr) can be separated by reversed-phase chromatography on RPC-5. 2. A cytoplasmic mutant has been isolated which lacks tRNA1Thr but has normal levels of tRNA2Thr. This mutation was previously shown to map between the oxi 1 and oxi 2 loci on mitochondrial DNA. 3. tRNA1Thr and tRNA2Thr hybridize to wild type mitochondrial but not nuclear DNA and are capable of partially competing with each other. Hybridization of each species to different segments of mitochondrial DNA isolated from p- clones indicate that there are two threonyl tRNA genes. One gene is located between oxi 1 and oxi 2 and codes for tRNA1Thr. The second gene codes for tRNA2Thr and is near the cap locus. 4. Binding assays to E. coli ribosomes indicate that tRNA2Thr recognizes the threonine triplet ACA and may also recognize the other three triplets but with a much lower efficiency. None of the four codons for threonine stimulate the binding of tRNA1Thr to the ribosomes.

Codon↗
PubMed1979

Sequence homologies of (guanosine + cytidine)-rich regions of mitochondrial DNA of Saccharomyces cerevisiae.

The nucleotide sequences of two distinct regions of mitochrondrial DNA of Saccharomyces cerevisiae are reported. The regions studied have a high content of G + C (45%) and contain closely spaced Hpa II and Hae III restriction sites. Both regions have sequences that are homologous over a lenght of 47 base-pairs. In addition, the two regions are highly palindromic. These data support certain aspects of the organization of mitochondrial DNA proposed by Prunell and Bernardi (Prunell, A., and Bernardi, G. (1977) J. Mol. Biol. 110, 53--74).

Base Sequence↗
PubMed1979

Assembly of the mitochondrial membrane system: sequences of yeast mitochondrial valine and an unusual threonine tRNA gene.

The mitochondrial DNA segments of two independently isolated rho- clones of S. cerevisiae carrying a genetic marker for a threonine tRNA have been characterized by restriction endonuclease analysis and DNA sequencing. The DNA sequences of the two segments have been used to deduce the primary and secondary structures of the tRNA. The threonine tRNA is unusual in having a leucine anticodon (3'-GAU-5'). Despite the anomalous anticodon, the tRNA is proposed to function in mitochondrial protein synthesis. One of the rho- clones contains an additional coding sequence that has been identified as a valine tRNA genes have been located on the wild-type physical map and determined to be transcribed from two different strands.

Base Sequence↗