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21.
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Codon Usage in Tetrahymena and Other Ciliates 总被引:6,自引:0,他引:6
DUANE W. MARTINDALE 《The Journal of eukaryotic microbiology》1989,36(1):29-34
Codon usage in ciliates was examined by analyzing the coding regions of 22 ciliate genes corresponding to a total of 26, 142 nucleotides (8, 714 codons). It was found that Tetrahymena, Paramecium and the hypotrichs ( Oxytricha and Stylonychia ) differed in which synonymous codons were used most frequently by their genes. In fact, the codon choices in highly expressed Tetrahymena genes were more similar to those of yeast genes than those of Paramecium genes. The ciliates do not appear to have unusually strong biases in codon usage frequency when compared to other protists such as yeast. The analysis of the Tetrahymena genes indicated that genes which are highly expressed during normal cell growth have a stronger bias towards using the "preferred" codons than those expressed at lower levels during growth or for brief periods during processes such as conjugation. This conforms to what is found in other protists. 相似文献
23.
The function of the N-terminal amino acids of Saccharomyces cerevisiae hexokinase II was studied in vivo using strains producing a form of hexokinase II lacking its first 15 amino acids (short form). This short form of hexokinase II was produced from a fusion between the promoter region of the PGK1 gene and the HXK2 coding sequence except the first 15 codons. As expected, the in vitro analysis of the short form protein by gel filtration chromatography indicates that the short protein does not form dimers under conditions where the wild-type protein dimerizes. Kinetic studies show that the enzymatic activities are very similar to wild-type behavior. The physiological experiments performed on the strains containing the fusion allele demonstrate that the short form of the enzyme is similar to the wild-type both in terms of phosphorylation of hexoses and glucose repression. We conclude that the N-terminal amino acids of hexokinase II are not required in vivo either for phosphorylation of hexoses or for glucose repression. 相似文献
24.
Based on similarities in basidial morphology and nucleotide sequences of the V3 variable region in the large sub-unit ribosomal RNA, the yeastLeucosporidium lari-marini is considered phylogenetically related to the genusCystofilobasidium. Therefore the new combinationCystofilobasidium lari-marini is proposed. 相似文献
25.
P. L. Bolen C. P. Kurtzman J. M. Ligon B. M. Mannarelli R. J. Bothast 《Antonie van Leeuwenhoek》1992,61(3):195-205
Five strains of the heterothallic yeastSaccharomycopsis crataegensis have been previously shown to contain DNA and/or RNA plasmidlike molecules (Shepherd et al. 1987). Three DNA plasmids, designated pScrl-1,-2 and -3, were found in strain NRRL Y-5902, while two were identified in each of NRRL strains Y-5903 and Y-5904. DNA plasmids were not identified inS. crataegensis strains Y-5910 or YB-192. FourS. crataegensis strains (Y-5903, Y-5904, Y-5910 and YB-192) were also shown to possess double-stranded RNA (dsRNA) molecules not found in strain Y-5902 (Shepherd et al. 1987). Hybridization studies now demonstrate the DNA plasmids in Y-5903 and Y-5904 to be highly homologous to their respective size counterparts (pScrl-1 and pScrl-2) in Y-5902 and to show some homology to pScrl-3. Restriction endonuclease mapping studies confirm the linear nature of each plasmid and establish identical restriction maps for a 1.4 kilobase (kb) region in pScrl-2 and -3. This 1.4 kb region accounts for the hybridization homology of pScrl-2 and pScrl-3 noted by Shepherd et al. (1987) and for homology of the plasmids of Y-5903 and Y-5904 to pScrl-3 of Y-5902. The pScrl plasmids show no homology to the dsRNA molecules ofS. crataegensis, the 2 M circular DNA ofStaccharomyces cerevisiae, the killer plasmids ofKluyveromyces lactis, or the linear DNA plasmids ofPichia inositovora.In crosses between linear DNA plasmid-containing and dsRNA-containing strains, only progeny containing the pScrl plasmids were recovered. Poor spore viability and a lack of complete tetrad recovery limited the extent of the analysis, but the findings suggest a cytoplasmic mode of inheritance for these linear DNAs.The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned. 相似文献
26.
Kaoru Nakamura Takehiko Miyai Kiyoko Inoue Seiji Kawasaki Shinzaburo Oka Atsuyoshi Ohno 《Biocatalysis and Biotransformation》1990,3(1):17-24
Esters of 3-methyl-2-oxobutanoic acid are reduced with bakers' yeast by three methods: free bakers' yeast in water, immobilized bakers' yeast in water, and immobilized bakers' yeast in hexane. Although (R)-hydroxy esters are obtained in all cases, the enantiomeric excess varies from 3% (reduction of the methyl ester with free bakers' yeast in water) to 93% (reduction of the butyl ester with immobilized bakers' yeast in hexane) depending on the structure of substrate and on the reaction conditions. The mechanism of the present stereochemical control is discussed. 相似文献
27.
28.
Summary During the growth of Kluyveromyces marxianus var. marxianus ATCC 10022 on lactose, peaks of glucose, but not -galactosidase activity, were detected iroculture medium. Harvested and washed whole cells produced glucose and galactose from lactose, or ortho-nitro-phenol from the chromogenic substrate ortho-nitro-phenyl--D-galactopyranoside (ONPG), indicating that -galactosidase is physically associated with cells. ONPG hydrolysis by whole cells presented a monophasic kinetics (Km 36.6 mM) in lactose exponential growth phase cells, but a biphasic kinetics (Km 0.2 and 36.6 mM) in stationary growth phase cells. Permeabilization with digitonin or disruption of cells from both growth phases led to monosite ONPG hydrolysis (Km 2.2 to 2.5 mM), indicating that =galactosidase is not located in the periplasm. In addition, the energy inhibitors fluoride or arsenate, as well as the uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP) prevented ONPG hydrolysis by whole cells. These findings indicate that energy coupled transmembrane transport is the rate-limiting step for intracellular ONPG cleavage. The taxonomic and physiologic implications of the exclusive intracellular location of -galactosidase of K. marxianus var. marxianus ATCC 10022 are discussed. 相似文献
29.
The heterobasidiomycetous yeastRhodotorula glutinis was able to grow in medium containing a high concentration of LiCl. This character ofR. glutinis was presumed to be attributable to its ability to incorporate [14C]-adenine and [14C]-leucine into nucleic acids and proteins, respectively, in the presence of LiCl. Intracellular levels of Li+ and Cl– ions, production and accumulation of glycerol as an osmoregulator, and respiration in the LiCl-stressed condition were almost the same in the tolerant yeastR. glutinis and the sensitive yeastRhodosporidium sphaerocarpum. 相似文献
30.
A new simple method for the preparation of chemically crosslinked chitosan beads is presented. It consists of the dropwise addition of 2-3% (w/v) low molecular weight chitosan solution containing 2% (w/v) glyoxal in 1% (w/v) tetrasodiumdiphosphate, pH 8.0. Immobilized viable baker's yeast (Saccharomyces cerevisiae) could be obtained via gel entrapment within the new beads when means preventing their direct contact with soluble chitosan were provided, "disguising" the cells until gelation and crosslinking were completed. Such means included cell suspension in castor oil or mixing with carboxymethyl-cellulose powder. Application of these means was shown to be necessary, as cells exposed to soluble chitosan immediately lost their viability and glycolytic activity. Yeast disguised in castor oil was also protected from bead reinforcement by glutaraldehyde treatment, significantly strengthening bead stability while operating under acidic conditions. This capability was demonstrated by continuous ethanol production by chitosan entrapped yeast. (c) 1994 John Wiley & Sons, Inc. 相似文献