Eukaryotic biology

Barboric M, PeterUn BM (2005) A new paradigm in eukaryotic biology HIV Tat and the control of transcriptional elongation. PLoS Biol 3 200-203... 

Glycoconjugates are the most functionally and structurally diverse compounds in Nature and it is now well established that protein- and lipid-bound saccharides play essential roles in many molecular processes impacting eukaryotic biology and disease.Examples of such processes include fertilization, embiyogenesis, neuronal development, hormone activities, the proliferation of cells and their organization into specific tissues. Remarkable changes in the cell-surface carbohydrates occur with tumor progression, which... 

In summary, CO has been shown play an essential role in eukaryotic biology and is a key molecule with respect to homeostasis. Many researchers have shown that CO as a gas or locked within a CO-RM can be... 

The electron transport protein, cytochrome c, found in the mitochondria of all eukaryotic organisms, provides the best-studied example of homology. The polypeptide chain of cytochrome c from most species contains slightly more than 100 amino acids and has a molecular weight of about 12.5 kD. Amino acid sequencing of cytochrome c from more than 40 different species has revealed that there are 28 positions in the polypeptide chain where the same amino acid residues are always found (Figure 5.27). These invariant residues apparently serve roles crucial to the biological function of this protein, and thus substitutions of other amino acids at these positions cannot be tolerated. 

Sefton, B., and Buss, J. E., 1987. The covalent modification of eukaryotic proteins widi Journal of Cell Biology 104 1449-1453. 

In contrast, RNA occurs in multiple copies and various forms (Table 11.2). Cells contain up to eight times as much RNA as DNA. RNA has a number of important biological functions, and on this basis, RNA molecules are categorized into several major types messenger RNA, ribosomal RNA, and transfer RNA. Eukaryotic cells contain an additional type, small nuclear RNA (snRNA). With these basic definitions in mind, let s now briefly consider the chemical and structural nature of DNA and the various RNAs. Chapter 12 elaborates on methods to determine the primary structure of nucleic acids by sequencing methods and discusses the secondary and tertiary structures of DNA and RNA. Part rV, Information Transfer, includes a detailed treatment of the dynamic role of nucleic acids in the molecular biology of the cell. 

In terms of evolutionary biology, the complex mitotic process of higher animals and plants has evolved through a progression of steps from simple prokaryotic fission sequences. In prokaryotic cells, the two copies of replicated chromosomes become attached to specialized regions of the cell membrane and are separated by the slow intrusion of the membrane between them. In many primitive eukaryotes, the nuclear membrane participates in a similar process and remains intact the spindle microtubules are extranuclear but may indent the nuclear membrane to form parallel channels. In yeasts and diatoms, the nuclear membrane also remains intact, an intranuclear polar spindle forms and attaches at each pole to the nuclear envelope, and a single kinetochore microtubule moves each chromosome to a pole. In the cells of higher animals and plants, the mitotic spindle starts to form outside of the nucleus, the nuclear envelope breaks down, and the spindle microtubules are captured by chromosomes (Kubai, 1975 Heath, 1980 Alberts et al., 1989). 

Fig. 3-8 A thin section showing a eukaryotic cell. Note the nucleus (N) is bound by a nuclear membrane. In the cytoplasm of the cell are many mitochondria (M) and intracytoplasmic membranes. (Reprinted with permission from Richard Rodewald, Univ. of Virginia/Biological Photo Service.)...

Many other peptides are synthesized as proproteins that require modifications before attaining biologic activity. Many of the posttranslational modifications involve the removal of amino terminal amino acid residues by specific aminopeptidases. Collagen, an abundant protein in the extracellular spaces of higher eukaryotes, is synthesized as procollagen. Three procol-... 

This subdivision is not based on the more usual macroscopic criteria it was made possible when techniques of subcellular biology became sufficiently refined for many more fundamental differences to become apparent. Some of the criteria differentiating eukaryotes and prokaryotes are given in Table 1.1. 

It was tempting to base the study of membrane transport in eukaryotic cells on similar simple principles. For this purpose, as well as for molecular biology as a whole, the yeast Saccharomyces cerevisiae appeared to be the best suited organism. From early times on, this yeast has occupied a privileged place for mankind. Due to... 

Several aryl esters of 6-chloromethyl-2-oxo-2//-l -benzopyran-3-carboxylic acid act as human Lon protease inhibitors (alternate substrate inhibitors)46 without having any effect on the 20S proteasome. Proteasomes are the major agents of protein turnover and the breakdown of oxidized proteins in the cytosol and nucleus of eukaryotic cells,47 whereas Lon protease seems to play a major role in the elimination of oxidatively modified proteins in the mitochondrial matrix. The coumarin derivatives are potentially useful tools for investigating the various biological roles of Lon protease without interfering with the proteasome inhibition. 

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