Cell, plant yeast

In addition to the catalytic action served by the snRNAs in the formation of mRNA, several other enzymatic functions have been attributed to RNA. Ribozymes are RNA molecules with catalytic activity. These generally involve transesterification reactions, and most are concerned with RNA metabofism (spfic-ing and endoribonuclease). Recently, a ribosomal RNA component was noted to hydrolyze an aminoacyl ester and thus to play a central role in peptide bond function (peptidyl transferases see Chapter 38). These observations, made in organelles from plants, yeast, viruses, and higher eukaryotic cells, show that RNA can act as an enzyme. This has revolutionized thinking about enzyme action and the origin of life itself. 

E. coli B. subtilis Pseudomonas sp. Yeasts Insect cells Mammalian cells Plants ... 

Gong, Z.Z. et al., A constitutively expressed Myc-like gene involved in anthocyanin biosynthesis from Perilla frutescens molecular characterization, heterologous expression in transgenic plants and transactivation in yeast cells. Plant Mol Biol, 41, 33, 1999. 

Ephedrine was originally isolated as the active agent present in plant extracts used in ancient Chinese medicine for respiratoiy ailments. As long ago as 1921 the formation of optically active phenylacetyl carbinol (PAC) from benzaldehyde and pyravate by brewers yeast and cell-free yeast extracts was reported. The PAC can then be reductively animated to produce optically active L-ephedrine (Figure 4.18). L-Ephedrine is widely used in the treatment of asthma and hay fever as a bronchodilating agent and decongestant. 

There are many glycosylation mutants of cultured mammalian cells and yeast. They have been selected as rare survivors of treatments that kill cells expressing a particular carbohydrate or glycoprotein at the cell surface. For example, plants produce a variety of proteins, called lectins, which bind to cell surface oligosaccharides. Lectins are toxic to mammalian cells. They can be used to select for mutants that no longer bind the lectin because they lack a particular carbohydrate at the cell surface. Such glycosylation mutants have low amounts of glycoproteins that require carbohydrates for stable expression. 

Three types of ribonucleotide reductase catalyze this reduction of the ribose ring. The most widely distributed in nature occurs in mammalian and plant cells, in yeast, and in some prokaryotes. This type of reductase contains a tyrosyl radical closely associated with nonheme iron, as in the reductase from E. coli. The E. coli reductase is composed of two nonidentical subunits, both contributing to the active site it is specific for the reduction of diphosphates (ADP, GDP, CDP, and UDP). 

Cytochrome oxidase (cytochrome aa3) represents the most important cytochrome of the a class. This is the terminal oxidase used in animals, plants, yeasts, algae and some bacteria. It contains two copper centres, giving four redox groups in total. This oxidase is discussed with other cytochromes that have a terminal oxidase function in Sections 62.1.12.4 and 62.1.12.5. These are cytochromes o, d and cd,. The oxidases fed719 and ax are not included in that discussion. The situation regarding cytochrome ax has been confused, partly due to uncertainty in the definition of this cytochrome. In some respects, the properties of cytochrome ax resemble those of mitochondrial and bacterial aa3. It functions as a terminal oxidase in some bacteria,720 but its role in E. coli is unknown. A soluble fraction from disrupted E. coli cells grown anaerobically on glycerol and fumarate contains a hemoprotein similar to cytochrome ax, which has catalase and peroxidase activity.721... 

The size of the genomic DNA in eukaryotic cells (such as the cells of yeast, plants, or mammals) is much larger (up to 10+11 base pairs) than in E. coli (ca. 10+6 base pairs). The rate of the eukaryotic replication fork movement is about fifty nucleotides per second, which is about ten times slower than in E. coli. To complete replication in the relatively short time periods observed, multiple origins of replication are used. In yeast cells, these multiple origins of replication are called autonomous replication sequences (ARSs). As with prokaryotic cells, eukaryotic cells have multiple DNA polymerases. DNA polymerase S, complexed with a protein called proliferating... 

Glycoproteins produced in nonhuman cells such as plant cells and yeast cells may have a modified glycan structure. Although natural antibodies exist that react with nonhuman glycan structures [18], there is no example of an immune reaction that was mounted to modified glycan structure of a therapeutic protein. 

Although bacterial nucleic acids and nucleoproteins have been recognized since the turn of the centuryonly the last decade has witnessed research on the low-molecular nucleotides and nucleosides in bacterial cells. Simultaneously, a variety of such substances from other materials (such as plants, yeasts, and animal tissues) have been isolated. Most of these substances are present in small amounts in the cell, and the introduction of refined techniques (such as ion-exchange chromatography, paper chromatography, and paper electrophoresis) were required for their isolation. The isotope technique has also contributed substantially to our knowledge of these substances. 

Prillinger H, Schweigkofler W, Lopandic K, Bauer R, Mueller UG Evolution of Asco- and Basidiomycota based on cell wall sugars, 18S ribosomal DNA sequences and coevolution with animals and plants. Yeast Newslett 1999 48 12. 

Many cells are susceptible to the appreciable shearing forces that arise on repeated freezing and thawing, or to hypotonic buffers which cause cells to swell up, and in certain cases to lyse this is particularly the case for cells in soft plant and animal tissue. Such treatments only rarely lead to complete cell lysis, the exceptions to this being erythrocytes and reticulocytes which are lysed quantitatively under hypotonic conditions. Non-mechanical homogenisation is of particular relevance to cells like yeast which are refractory to other procedures. One of the simplest procedures for yeast, which can certainly not be described as gentle, is toluene-induced autolysis. This is carried out at room temperature and leads to permeabilisation of the cell walls this causes various hydrolases to be activated causing breakdown not only of the cell structure, but also (undesirably) of many sensitive proteins and nucleic acids in the cell. Consequently, this process is mainly of historical interest. 

The lysosomal acid sphingomyelinase (aSMase) isoform is inhibited by L-camitine, a cofactor of acyl-coenzyme A transport in mitochondria (107, 108), and by phosphatidylinositol polyphosphates, which occur in plant, yeast, and mammalian cells (109). 

Mammalian Insect cells Bacteria Yeast Animals Plants... 

Animals Plants Yeast Mammalian Insect cells Bacteria... 

The function of LPPG has yet to be determined. Analogous glycolipids have been described in plants, yeast and fungi and may be functionally similar to gangliosides in higher eukaryotes (13). Whether LPPG serves in any capacity in parasite-host cell interactions is unknown. 

Baciphelacin is toxic to HeLa cells and a study of its mechanism of action revealed that it was a potent inhibitor of protein synthesis (ref.121). A 50% inhibition of protein synthesis in HeLa cells was found at a concentration around 10" M (0.042 ig/ml). This compound is unusual and interesting because it blocks translation only in animal cells and not in plant, yeast or Escherichia coli systems. Translation inhibitors are usually blockers of eukaryotic and/or prokaryotic systems not animal cells only. In a study of related compounds 4-acetyl-6,8-dihydroxy-5-methyl-3,4-dihydroisocoumarin was found to block translation in HeLa cells but not in yeast cells. Interestingly, the saturated... 

Fig. 3 SWOT analysis of plant expression systems. Plant expression systems have a lot of advantages (plus) over other systems and are therefore mostly shown on the right-hand side of the picture (Raskin I et al., Plants and human health in the twenty-first century. Trends In Biotechnol. 2002 20, 522-531.). Herein different systems (transgenic animals, mammalian cell culture, plants, yeast, and bacteria) are compared in terms of speed (how quickly they can be developed), operating and capital costs...

Acid Metabolism of Yeast Cells," Plant Physiol. 26 189 (1967). 

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