Proteins biosynthesis, ribosomal, antibiotic inhibitor

Macrolides, lincosamides and streptogramins are protein biosynthesis inhibitors that bind to 50S subunit of the ribosome and inhibit peptidyl tRNA translocation from the A-site to the P-site." Macrolides have a glycosylated 14-, 15- or 16-membered lactone ring structure and are produced by several species of Streptomyces. Lincosamide antibiotics were isolated initially from Streptomyces lincolnensis but later isolated from different species of Streptomcyces. Streptogramins were also isolated from Streptomycesgraminofaciens and subsequently from several different Streptomyces species. There are two structurally different streptogramins, A and B they are bacteriostatic individually and can be bactericidal when combined. 

More than 500 different representatives of the macrolide antibiotics are known, most of which are biologically active against Gram-positive bacteria, displaying a relatively low toxicity. Clinically used are erythromycin, oleandomycin, carbomycin and leucomycin (O Fig. 5). They act as inhibitors of the bacterial protein biosynthesis by binding to the 50S-ribosomal subunit. The synthesis of the two clinically important 16-membered ring macrolide antibiotics leucomycin A3 and carbomycin B could be started from D-glucose, which was chosen because it contained three of the required stereocenters [40]. 

How are the outer membrane proteins described above or the other E. coli envelope proteins biosynthesized in the cell Even though they must be made on ribosomes, it is not known whether they are synthesized in exactly the same manner as cytoplasmic proteins. One approach to this question is to examine and compare the effects of various antibiotic inhibitors of protein synthesis on the biosynthesis of membrane and cytoplasmic proteins. 

Peptide biosynthesis may occur through two different systems. Most of cellular peptides and proteins are produced by the ribosomal machinery connecting 20 proteino-genic amino acids to the desired products. However, most of the bioactive peptides are produced non-ribosomally by large peptide synthetases. These peptides are used as antibiotics, enzyme inhibitors, toxins, and other medically useful drugs. The biosynthesis of... 

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