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N C Martin

Publications and source records attributed to N C Martin.

86 records · Page 5Linked to original sources
PubMed1980

Characterization of tRNA genes in tRNA region II of yeast mitochondrial DNA.

We have isolated individual mitochondrial tRNAs from a petite mutant OI-P2-1 known to contain a limited subset of mitochondrial tRNA genes and have mapped these genes on the wild type genome of the yeast strains MH41-7B and D273-10B. To obtain DNA for fine structure mapping and DNA sequence analysis of these genes, we screened a yeast mitochondrial DNA-pBR322 recombinant bank with the isolated tRNAs. We report here the fine structure mapping of recombinant clones containing the tryptophan, formyl methionine and proline tRNA genes as well as the DNA sequence of the proline tRNA gene. The combination of restriction mapping and DNA sequence analysis has enabled us to locate these genes precisely on the wild type genome and to determine their direction of transcription.

Base Sequence↗
PubMed1980

Yeast mitochondrial tRNATrp can recognize the nonsense codon UGA.

DNA sequence analysis of mitochondrial genes that code for some mitochondrial proteins has suggested that the opal terminator, UGA, is used as a sense codon in mitochondria. The complete sequences of both the yeast and human genes coding for cytochrome oxidase subunit II contain UGA codons in the reading frame. When the protein sequences predicted by these DNA sequences are compared with the known protein sequence of bovine mitochondrial cytochrome oxidase subunit II, there are regions of homology, in which UGA codons correspond to tryptophan residues. Therefore it has been suggested that UGA specifies tryptophan in the mitochondrial code. We have isolated a yeast mitochondrial tRNATrp and used it to locate the mitochondrial tRNATrp gene in pBR322-mitochondrial DNA recombinants. DNA sequence analysis of this gene revealed that the mitochondrial tRNATrp anticodon is 5'UCA3'. Because there is a U in the wobble position, this tRNA can recognize and insert tryptophan into a growing polypeptide chain in response to the nonsense codon UGA.

Anticodon↗
PubMed1980

Nucleotide sequence of the mitochondrial genes coding for tRNAglyGGR and tRNAvalGUR.

Yeast mitochondrial DNA-pBR322 recombinant DNA molecules known to contain tRNA genes from a tRNA rich region of the yeast genome were used as a source of DNA for restriction mapping and tRNA gene sequence analysis. We report here restriction maps of two segments of yeast mitochondrial DNA and the sequence of mitochondrial genes coding for tRNAglyGGR and tRNAvalGUR. Both genes are flanked by A + T rich DNA and neither has an intervening sequence nor codes for a 3' CCA end. The tRNA structures deduced from the genes have the usual cloverleaf structures and invariant nucleotides. This combination of DNA sequencing and restriction mapping has enabled us to determine that the tRNAvalGUR and a previously sequenced tRNA, the tRNApheUUY are transcribed from the same strand of DNA.

Base Sequence↗
PubMed1980

The tRNAAGYSer and tRNACGYArg genes from a gene cluster in yeast mitochondrial DNA.

Yeast mitochondrial DNA-pBR322 recombinant DNA molecules screened for rRNA genes were used as a source of DNA for mitochondrial tRNA gene sequence analysis. We report here the sequences of yeast mitochondrial tRNA genes coding for a tRNAAGYSer and a tRNACGYArg. The tRNAAGYSer sequence deduced from the gene is the first reported sequence of a yeast tRNAAGYSer. It is also the second yeast mitochondrial tRNASer gene to be sequenced, and demonstrates unequivocally the presence of mitochondrial encoded serine tRNA isoacceptors. The tRNACGYArg sequence deduced from the gene is the most AT-rich (82%) tRNA sequence ever reported. Whereas all the mitochondrial genes sequenced to date exist singly on the genome and are separated by long stretches of AT-rich DNA, the tRNAACYSer and tRNAcgyarg genes exist in tandem, separated by only 3 bp. This gene arrangement strongly suggests that mitochondrial tRNA genes may be transcribed into multicistronic precursors.

Base Sequence↗
PubMed1979

Sequence analysis of two yeast mitochondrial DNA fragments containing the genes for tRNA Ser UCR and tRNA Phe UUY.

Two restriction enzyme fragments containing yeast mitochondrial tRNA genes have been characterized by DNA sequence analysis. One of these fragments is 320 base pairs long and contains a tRNA Ser gene. The corresponding tRNA SER was isolated from yeast mitochondria and its nucleotide sequence also was determined. This mitochondrial tRNA is 90 nucleotides in length, has a G + C content of 38%, and has UGA as the anticodon. A portion of a 680-base-pair DNA fragment containing a tRNA Phe gene was also sequenced. The portion of this gene which codes for the mature tRNA is 75 base pairs in length, has a G + C content of 33%, and contains the anticodon GAA. Neither gene contains an intervening sequence or codes for the 3' CCA terminus. Both are surrounded by regions of more than 90% A + T. The significance of these sequences is discussed.

Base Sequence↗
PubMed1978

Physical mapping of genes on yeast mitochondrial DNA: localization of antibiotic resistance loci, and rRNA and tRNA genes.

We have physically mapped the loci conferring resistance to antibiotics that inhibit mitochondrial protein synthesis (erythromycin, chloramphenicol and paromomycin) or respiration (oligomycin I and II), as well as the 21s and 14s rRNA and tRNA genes on the restriction map of the mitochondrial genome of the yeast Saccharomyces cerevisiae. The mitochondrial genes were localized by hybridization of labeled RNA probes to restriction fragments of grande (strain MH41-7B) mitochondrial DNA (mtDNA) generated by endonucleases EcoRI, HpaI, BamHI, HindIII, SalI, PstI and HhaI. We have derived the HhaI restriction fragment map of MH41-7B mit DNA, to be added to our previously reported maps for the six other endonucleases. The antibiotic resistance loci (antR) were mapped by hybridization of 3H-cRNA transcribed from single marker petite mtDNA's of low kinetic complexity to grande restriction fragments. We have chosen the single Sal I site as the origin of the circular physical map and have positioned the antibiotic loci as follows: C (99.5-1.Ou)--P (27-36.Ou)--OII (58.3-62u--OI (80-84u)--E (94.4-98.4u). The 21s rRNA is localized at 94.4-99.2u, and the 14s rRNA is positioned between 36.2-39.8u. The two rRNA species are separated by 36% of the genome. Total mitochondrial tRNA labeled with 125I hybridized primarily to two regions of the genome, at 99.5-11.5u and 34-44u. A third region of hybridization was occasionally detected at 70--76u, which probably corresponds to seryl and glutamyl tRNA genes, previously located to this region by petite deletion mapping.

Chloramphenicol↗
PubMed1977

Yeast mitochondrial DNA specifies tRNA for 19 amino acids. Deletion mapping of the tRNA genes.

We have previously identified 14 aminoacyl tRNAs that are specified by yeast mitochondrial DNA (mtDNA). We now report four more amino acids (Arg, Cys, Trp, Thr) that acylate tRNAs which hybridize with mtDNA. Furthermore one of the two mitochondrial tRNAs that we had earlier demonstrated to be directly charged with glutamic acid responds to glutamine but not to glutamic acid codons. Thus Gln-tRNAGln appears to be formed by transamidation of a missense intermediate Glu-tRNAGln. This brings to 19 the number of amino acids which have corresponding tRNAs specified by mtDNA. Only tRNAAsn has not yet been shown to be a mtDNA transcript. We have also mapped the genes for the newly identified mitochondrial tRNAs, as well as several others that were previously identified but unmapped, by hybridization to the mtDNA of a series of petite deletion mutants. We now have ordered 20 mitochondrial tRNA genes (including two methionyl-tRNAs) wtih respect to the antibiotic resistance markers chloramphenicol (CR), erythromycin (ER), paromomycin (PR), and oligomycin I and II (ORI, ORII). Eighteen tRNA genes map between the C and E resistance markers. Only the serinyl-tRNA and glutamyl-tRNA genes are localized near the OI and OII resistance markers.

Amino Acyl-tRNA Synthetases↗
PubMed1975

Surgical treatment of typhoid perforation.

The treatment of perforation of the ileum in 50 cases of typhoid fever is reviewed. Because of the risk of reperforation after surgical closure of a perforation, wedge excision of the ulcer if there is a single area of diseases bowel or segmental resection of the ileum if the ileum is more extensively affected are recommended.

Adolescent↗
PubMed1975

Gametic differentiation in Chlamydomonas reinhardtii. I. Production of gametes and their fine structure.

Gametogenesis in Chlamydomonas reinhardtii has been studied in mating-type plus cells utilizing several different culture conditions, all of which are shown to depend on the depletion of nitrogen from the medium, and the fine structure of gametes prepared under these conditions has been compared by using thin sections of fixed materials. We document alterations in ribosome levels, in chromatin morphology, in starch levels, in the organization of chloroplast membranes, and in the appearance of nuclear envelope and endoplasmic reticulum membranes during gametogenesis. We also noted the acquisition of two new organelles: a mating structure (Friedman, L., A. L. Colwin, and L. H. Colwin. 1968. j. cell Sci. 3:115-128; goodenough, U. W., and R. L. Weiss. 1975. J. Cell Biol. 67:623-637), and Golgi-derived vesicles containing a homogeneous material. We chart the time course of these morphological changes during synchronous gametogenesis. We note that many of these changes may represent adjustments to nitrogen starvation rather than direct features of gametic differentiation, and we also document that cells can differentiate so that they survive conditions of nitrogen starvation for many weeks after they become gametes. We conclude that metabolic alterations, the acquisition of mating ability, and the preparation for long-term survival are all elicited in this organism by nitrogen withdrawal, and we discuss how the various structural alterations observed in this study may relate to these three interrelated avenues of cellular differentiation.

Carbon Dioxide↗
PubMedDate not supplied

The sensitivity and specificity of red-starch paper for the detection of saliva.

The detection of saliva in forensic casework is extremely important in many types of cases. This study describes a relatively sensitive method, based on a red dye bound to starch, for the detection of amylase. The sensitivity and specificity of the method has been examined by testing over 50 household products, various body fluids and five laboratory chemicals. This study demonstrated for the first time that positive results can be obtained from certain washing powders as well as other household products. As well as detecting amylase in saliva, positive Red-Starch results were obtained from faeces and urine. The method was found to be suitable for the detection of mixtures of saliva and semen in conjunction with the Brentamine test for the detection of acid phosphatase.

Amylases↗