Ribosomal sites

There are numerous examples of the inhibition of biosynthesis by fungicides. Some fungicidal secondary metabolites, like cyclohexi-mide and blasticidine, interfere with synthesis of peptide bonds at the ribosomal site (2). Another, kasugamycine, influences aminoacyl-t-RNA/ribosome interactions (3). Finally, another mechanism inhibiting protein biosynthesis is realized on the DNA/RNA- level by the... 

Tagging a ribosomal site. Design an affinity-labeling reagent for one of the tRNA binding sites in E. coli ribosomes. 

This RNA-paromomycin structure also explains a number of features that help show why modification of the aminoglycoside antibiotic by the resistance enzymes prevents the modified drug from binding to the ribosomal site. These features are as follows. 

Ribosomes sites where protein synthesis takes place... 

During Chain Elongation Each Incoming Aminoacyl-tRNA Moves Through Three Ribosomal Sites... 

The translation step where proteins are assembled following the code of messenger RNA has a few instances of inhibition by alkaloids [361]. Emetine and tubulosine block peptide bond formation, acting similarly to the antibiotic cycloheximide by blocking translocation of the growing peptide chain from the A site to the P site of the ribosome. They evidently bind to a specific ribosomal site [362]. Homoharringtonine may act similarly [363]. Lycorine may act at the level of termination [364]. Narciclasine and related alkaloids of the Amaryllidaceae prevent binding of the 3 end of aminoacyl-tRNA to the peptidyl transferase site of the ribosome [365, 366]. Mescaline may act similarly [367]. 

The ribosomal protein biosynthetic machinery encompasses all three types of modnlarity. The ribosome catalyst can be separated from the element determining the snbstrate specificity, i.e. the mRNA template. The two acylated tRNA snbstrates for the peptide-bond formation bind to different ribosomal sites, the A and P sites, and the mnltistep pathway catalyzed by the modnlar system may be reprogrammed by codon choice. 

Nature can also be used to form computers (Hayes, 2001). Messenger RNA (mRNA, see Section 5.3) causes proteins to be formed at ribosome sites. Before mRNA can be transcribed from genetic codons, an enzyme, RNA polymerase, must be present. RNA polymerase is blocked from its activity by a repressor protein, which binds to the DNA downstream from the target codon and... 

It is beyond the scope of this chapter to describe in detail the conditions used to define the binding of tRNA to the various ribosomal sites, since they must be optimized for each tRNA species and mRNA used,... 

Ribosome Site for protein synthesis consisting of RNA and protein, located in the cytoplasm. 

Since all the enzymic activities tested, including the sulfotransferase, were present in both rough and smooth microsomes, it was further postulated that, following synthesis at ribosomal sites, the enzymes move in their membrane-bound form through the smooth endoplasmic reticulum toward the Golgi zone. This assumption seems quite justified, since a flow of both membranes and certain enzymes has indeed been previously documented (Dalhier el al., 1966 Omura d. al., 1967). Tiereas the turn-... 

The conformational change in the anticodon loop has been suggested to be an important event in protein biosynthesis (Woese, 1970 Lake, 1977). Thus in the Lake (1977) model, the anticodon conformation switches fi om a S stack to a 3 stack, after the correct recognition of the tRNA in the ribosome site. This would presumably allow the aminoacyl group to move toward the ribosome-bound peptidyl-tRNA. 

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