Eukaryotic cells, stress-70 proteins

Mechanosensing is postulated to involve many different cellular and extracellular components. Mechanical forces cause direct stretching of protein-cell surface integrin binding sites that occur on all eukaryotic cells. Stress-induced conformational changes in the extracellular matrix may alter integrin structure and lead to activation of several secondary messenger pathways within the cell. Activation of these pathways leads to altered reg-... 

What are the mechanisms by which trichothecenes exert their transcriptional and post-transcriptional effects The 60S ribosomal subunit is a well-known molecular target of trichothecenes in leukocytes and other actively proliferating eukaryotic cells,3 whereas attempts to demonstrate alternative receptors have not been successful.37 38 Translational inhibitors that bind to ribosomes rapidly activate mitogen-activated protein kinases (MAPKs) and apoptosis via a mechanism termed the ribotoxic stress response. 39-40... 

On the other hand, several ROS are highly cytotoxic. Consequently, eukaryotic cells have developed an elaborate arsenal of antioxidant mechanisms to neutrahze their deleterious effects (enzymes such as superoxide dismutases, catalases, glutathione peroxidases, thioredoxin inhibitors of free-radical chain reaction such as tocopherol, carotenoids, ascorbic acid chelating proteins such as lactoferrin and transferrin). It can be postulated that ROS may induce an oxidative stress leading to cell death when the level of intracellular ROS exceeds an undefined threshold. Indeed, numerous observations have shown that ROS are mediators of cell death, particularly apoptosis (Maziere et al., 2000 Girotti, 1998 Kinscherf et al., 1998 Suzuki et al., 1997 Buttke and Sanstrom, 1994 Albina et al., 1993). 

A group of proteins that are synthesized by plant cells, prokaryotic cells, and eukaryotic cells in response to cold stress. It has been suggested that cold-shock proteins (CSPs) function as chaperones for mRNA. See Graumann, P.L. and Marshiel, M. A., A superfamily of proteins that contain the cold-shock domain, Trends Biochem. Sci. 23,286-290,1998 Phadtare,... 

Analyses of in situ DNA synthesis of Euglena gracilis identify zinc-dependent steps in the eukaryotic cell cycle and show that the derangements in RNA metabolism are critical determinants of the growth arrest associated with zinc deficiency. Combined use of microwave-induced emission spectrometry and micro gel emulsion chromatography shows the presence of stoichiometric amounts of zinc essential to the function of E. gracilis and yeast RNA polymerases, the reverse transcriptases" from avian myeloblastosis, murine leukemic and woolly type C viruses, and E. coli methionyl tRNA synthetase. These results stress the importance of zinc to both nucleic acid and protein metabolism. Transient-state kinetic studies of carboxypeptidase A show that zinc functions in the catalytic step of peptide hydrolysis and in the binding step of ester hydrolysis. 

When exposed to heat shock or other types of stress, a large number of prokaryotic and eukaryotic cells synthesize a small family of proteins that have been termed heat shock proteins. These proteins complex with many other proteins, and a wide variety of physiological and molecular functions have... 

Sucrose is a compatible osmolyte, belonging to a class of low molecular weight compounds (C12H22O11) present both in prokaryotic and eukaryotic cells in order to protect proteins against aggressive effects of harsh environmental conditions such as cold and heat stress [1,2],... 

In addition to the MAP kinases discussed above, both yeasts and higher eukaryotic cells contain other members of the MAP kinase superfamily. These Include mammalian Jun N-terminal kinases (JNKs) and p38 kinases, which become activated by various types of stresses, and six yeast kinases described below. Collectively referred to as MAP kinases, all these proteins are serlne/threonlne kinases that are activated in the cytosol in response to specific extracellular signals and then translocate to the nucleus. Activation of all known MAP kinases requires phosphorylation of both a tyrosine and a... 

Next, the authors turn to membrane proteins, the major functional constituents of biological membranes. The arrangement of proteins and lipids in membranes is described and the asymmetric, fluid nature of membranes is stressed. The important differentiation between integral and peripheral membrane proteins is discussed as well as the chemical forces that bind them to the membrane. The high-resolution analyses of the structures of selected membrane proteins are discussed, including structure prediction of membrane-spanning proteins. The chapter concludes with a discussion of internal membranes within eukaryotic cells and the mechanisms by which proteins are targeted to specific compartments within cells. 

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