Messenger synthesis

Interference with signal transduction by reducing second-messenger synthesis through. 

Variability in hormonal response patterns does not stop at the level of second-messenger synthesis. Thus, cyclic AMP can activate the well-known cAMP-dependent protein kinase A, but the possibility of other cAMP-respon-sive enzymes or cAMP-activated regulatory proteins should not be ruled out. The protein kinase activated by cAMP can activate a number of other enzymes. For example, in the liver, phosphorylase kinase (see fig. 24.15) is activated and catalyzes the breakdown of glycogen. In adipocytes, triacyl-glycerol lipase is activated and catalyzes the breakdown of triacylglycerols. 

J. Insulin second messengers synthesis of 6-0-(2-amino-2-deoxy-a-D-glucopyrano-sylJ-D-chiro-inositol-l-phosphate. Tetrahedron, Lett., 1993, 34, 7869-7872. 

Considerations of initiation of lac messenger RNA synthesis are directly related to the problems of induction (see Section IV). Since within 90 seconds of induction, enzyme appears, initiation of messenger synthesis must be rapid. The relative abundance of various messengers in the cell may be a function of the rate of initiation of RNA synthesis. For different RNA s the initiation rates vary by a wide margin. Thus initiation rates for ribosomal and tRNA synthesis in rapidly growing E. coli at 30°C range from 0.5 to 1 initiation per second [36], as contrasted with an initiation rate for the tryptophan operon mRNA of 1 every 2 to 5 minutes [37,38]. 

In this case, where the messenger half-life is about 2 minutes (see Section III, A, 6), the long duration of the increased penicillinase synthesis must indicate prolonged penicillinase messenger synthesis and a lag in the production or action of new repressor. A key experiment is illustrated in Fig. 5. Csanyi [29] tested the specific activity of cells in-... 

Bolle, A., Epstein, R. H., Salser, W., Geiduschek, E. P. Transcription during bacteriophage T4 development Requirements for late messenger synthesis. J. molec. Biol. 33, 339-362 (1968b). 

Cellular protein biosynthesis involves the following steps. One strand of double-stranded DNA serves as a template strand for the synthesis of a complementary single-stranded messenger ribonucleic acid (mRNA) in a process called transcription. This mRNA in turn serves as a template to direct the synthesis of the protein in a process called translation. The codons of the mRNA are read sequentially by transfer RNA (tRNA) molecules, which bind specifically to the mRNA via triplets of nucleotides that are complementary to the particular codon, called an anticodon. Protein synthesis occurs on a ribosome, a complex consisting of more than 50 different proteins and several stmctural RNA molecules, which moves along the mRNA and mediates the binding of the tRNA molecules and the formation of the nascent peptide chain. The tRNA molecule carries an activated form of the specific amino acid to the ribosome where it is added to the end of the growing peptide chain. There is at least one tRNA for each amino acid. 

Messenger RNA (mRNA) serves to carry the information or message that is encoded in genes to the sites of protein synthesis in the cell, where this information is translated into a polypeptide sequence. Because mRNA molecules are transcribed copies of the protein-coding genetic units that comprise most of DNA, mRNA is said to be the DNA-like RNA. ... 

Messenger RNA (mRNA) carries genetic messages from DNA to ribosomes, small granular particles in the cytoplasm of a cell where protein synthesis takes place. 

The regulation of receptor synthesis is a second component of receptor downregulation. It involves processes that reduce gene transcription, mRNA stability, and receptor half-life time. It should be noted that mechanisms in addition to the regulation of the receptor number may account for tolerance development. Second messenger levels and enzyme activities that participate in the signaling of a given receptor are... 

The infectious cycle of a (+)-strand RNA virus such as the hepatitis C virus differs by the fate of the viral RNA genome in the infected cell. Upon entry into the cell, the HCV genome is used as a messenger RNA to drive the synthesis of a large polyprotein precursor of about 3,000 residues [2]. The structural proteins are excised from the precursor by host cell signal peptidase. 

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