Protein synthesis translocation

It is possible that, over these longer periods, protein synthesis is affected. Itai Vaadia (1965, 1971) showed that during water stress cytokinin activity in the root exduate and translocation of cytokinin were reduced. Ben-Zioni, Itai Vaadia (1967) showed that the lower rate of protein synthesis of stressed leaf tissue could be raised by treatment of leaf material with kinetin. We need more information on levels of various proteins after naturally occurring stress. 

Fig. 8.4 Outline of the main events in protein synthesis initiation, elongation, translocation and termination. AUG is an initiation codon on the mRNA it codes for Af-fomiylmelhionine and initiates the formation of the 70S rihosome. UAG is a termination codon it does not code for any amino acid and brings about termination of protein synthesis.

Dominguez, J. M., Gomez-Lorenzo, M. G., and Martin, J. J. (1999). Sordarin inhibits fungal protein synthesis by blocking translocation differently to fusidic arid. j. Biol. Chem. 274, 22423-22427. 

Davis FI, Squire LR (1984) Protein synthesis and memory a review. Psychol Bull 96 518-559 Deisseroth K, Heist EK, Tsien RW (1998) Translocation of calmodulin to the nucleus supports CREB phosphorylation in hippocampal neurons. Nature 392 198-202 Dinerman J, Dawson TM, Schell MJ, Snowman A, Synder SH (1994) Endothelial nitric oxide synthase localized to hippocampal pyramidal cells implications for synaptic plasticity. Proc Natl Acad Sci U S A 91 4214-4218... 

Macrolides bind to the SOS ribosomal subunit of bacteria but not to the SOS mammalian ribosome this accounts for its selective toxicity. Binding to the ribosome occurs at a site near peptidyltransferase, with a resultant inhibition of translocation, peptide bond formation, and release of oligopeptidyl tRNA. However, unlike chloramphenicol, the macrolides do not inhibit protein synthesis by intact mitochondria, and this suggests that the mitochondrial membrane is not permeable to erythromycin. 

Emetine and dehydroemetine are natural alkaloid obtained from Cephaelis ipecacuanha and synthetic analog respectively. They are effective against tissue trophozoites of . histolytica. It has no effect on cysts but effective in amoebic liver abscess also. It acts by inhibiting protein synthesis by arresting intraribosome translocation of tRNA-amino acid complex. Dehydroemetine is less toxic than emetine and very effective drug for tissue amoebiasis. It is more rapidly eliminated from the body than emetine. 

Transketolase 733,736 Translation of genetic information, 5. See also Protein synthesis definition of 5 nick 257 regulation of 536 Translocation... 

Overview of reactions in protein synthesis. (aab aa2, aa3 = amino acids l, 2, 3.) Protein synthesis requires transfer RNAs for each amino acid, ribosomes, messenger RNA, and a number of dissociable protein factors in addition to ATP, GTP, and divalent cations. First the transfer RNAs become charged with amino acids, then the initiation complex is formed. Peptide synthesis does not start until the second aminoacyl tRNA becomes bound to the ribosome. Elongation reactions involve peptide bond formation, dissociation of the discharged tRNA, and translocation. The elongation process is repeated many times until the termination codon is reached. Termination is marked by the dissociation of the messenger RNA... 

This reaction is reversible when conducted in vitro, but under the conditions of pH and nicotinamide concentration that exist in the cell, it is irreversible. Thus, diphtheria toxin kills cells by irreversibly destroying the ability of EF-2 to participate in the translocation step of protein synthesis elongation. A number of other protein toxins have subsequently been found to ADP-ribosylate and inactivate cellular proteins involved in other essential cellular pathways. For example, cholera and pertussis toxins ADP-ribosylate and inactivate proteins important to cAMP metabolism. 

The enzymatic specificity of diphtheria toxin deserves special comment. The toxin ADP-ribosylates EF-2 in all eukaryotic cells in vitro whether or not they are sensitive to the toxin in vivo, but it does not modify any other protein, including the bacterial counterpart of EF-2. This narrow enzymatic specificity has called attention to an unusual posttranslational derivative of histidine, diphthamide, that occurs in EF-2 at the site of ADP-ribosylation (see fig. 1). Although the unique occurrence of diphthamide in EF-2 explains the specificity of the toxin, it raises questions about the functional significance of this modification in translocation. Interestingly, some mutants of eukaryotic cells selected for toxin resistance lack one of several enzymes necessary for the posttranslational synthesis of diphthamide in EF-2 that is necessary for toxin recognition, but these cells seem perfectly competent in protein synthesis. Thus, the raison d etre of diphthamide, as well as the biological origin of the toxin that modifies it, remains a mystery. 

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