Eukaryote origin

Many polysaccharides of eukaryotic origin show non-specific anti-viral activity and this property may be shared by some of the exopolysaccharides. The structural requirements for activity are not immediately evident as the polysaccharides exhibiting this activity are very diverse. 

Fig. 10.11 The modified tree of life still has the usual tree-like structure and also confirms that the eukaryotes originally took over mitochondria and chloroplasts from bacteria. It does, however, also show a network of links between the branches. The many interconnections indicate a frequent transfer of genes between unicellular organisms. The modified tree of life is not derived, as had previously been assumed, from a single cell (the hypothetical primeval cell ). Instead, the three main kingdoms are more likely to have developed from a community of primitive cells with different genomes (Doolittle, 2000)...

Most frequently, extracts of either prokaryotic or eukaryotic origin as such from Escherichia coli, wheat germ or rabbit reticulocytes are employed for cost reasons and availability. While those based on E. coli are unable of post-translational protein modification, eukaryotic extracts do allow synthesis of glycosylated or phosphorylated proteins to some extent when additional components, such as microsomes for glycosylation are added. Care needs to be taken with cell-free systems recombinated from the individual components when a native protein is to be produced that does not fold spontaneously... 

Initiation of protein synthesis involves the assembly of the components of the translation system before peptide bond formation occurs. These components include the two ribosomal subunits, the mRNA to be translated, the aminoacyl-tRNA specified by the first codon in the message, GTP (which provides energy for the process), and initiation factors that facilitate the assembly of this initiation complex (see Figure 31.13). [Note In prokaryotes, three initiation factors are known (IF-1, IF-2, and IF-3), whereas in eukary- otes, there are at least ten (designated elF to indicate eukaryotic origin).] There are two mechanisms by which the ribosome recognizes the nucleotide sequence that initiates translation ... 

One of the pathways for the biosynthesis of phos-phatidic acid in eukaryotes originates with dihy-... 

Bell, S. P., and B. Stillman, ATP-dependent recognition of eukaryotic origins of DNA replication by a multiprotein complex. Nature 357 128-134, 1992. 

Zillig W, Klenk HP, Palm P, Leffers H, Puhler G, Gropp F, Garrett RA (1989) Did eukaryotes originate by a fusion event Endocyt Cell Res 6 1-25... 

Genic Scale, Tempo, and Timing of Mitochondrial Enslavement and Eukaryote Origin... 

Van Valen LM, Maiorana VC (1980) The archaebacteria and eukaryotic origins. Nature 287 248-250... 

First, it is possible that enzymes of aerobic and anaerobic energy metabolism found in mitochondrion-related organelles of present-day eukaryotes originated with the a-proteobacterial symbiont that gave rise to mitochondria (Fig. 10.5, top), which could have been a facultative aerobe (e.g. Martin and Muller 1998 and Rotte et al. 2000 provide a biochemical rationale for this view). After the initial symbiotic integration of the mitochondrial ancestor, many endosymbiont genes were transferred to the nucleus, some of which were... 

Lower-case letters denote prokaryotic origin, upper-case letters denote eukaryotic origin. 

Different in vitro translation systems are used depending on whether the mRNA is of prokaryotic or eukaryotic origin. For eukaryotic mRNA, translation kits from reticulocyte lysates or wheat germ extract are recommended, and for prokaryotic mRNA, the E. coli 30 S supernatant, all of which are commercially available. These translation kits can be supplemented with [3H]-leudne or... 

The WD-repeat-containing proteins form a very large family that is diverse in both its function and domain structure. Within all these proteins the WD-repeat domains are thought to have two common features the domain folds into a beta propeller and the domains form a platform without any catalytic activity on which multiple protein complexes assemble reversibly. The fact that these proteins play such key roles in the formation of protein-protein complexes in nearly all the major pathways and organelles unique to eukaryotic cells has two important implications. It supports both their ancient and proto eukaryotic origins and supports a likely association with many genetic diseases. 

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