Streptogramin A antibiotics

Chemistry and biology of the 23-membered macrocydic streptogramin A antibiotics 07MRO159. 

Acetyl-CoA is also utilized as a cofactor to modify chloramphenicol by O-acetyltranferases (CATs). These enzymes have been found in many different bacterial genera and are usually plasmid encoded in clinical isolates. Furthermore, streptogramin type A antibiotics are acetylatedby Vat enzymes that occur on plasmids in staphylococci and enterococci. 

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. 

Pechere J-C (1996) Streptogramins a unique class of antibiotics. Drugs 51(Suppl 1), 13-19. 

The lincosamides, lincomycin and clindamycin are active against Grampositive bacteria. Plasmid-mediated inactivation from enzymatic nucleo-tidylation occurs in some staphylococci. Plasmid-encoded enzymes can modify streptogramin A (O-acetyltransferase enzyme) and streptogramin B (hydrolase enzyme involved) in S. aureus [198, 199], There is no evidence that bacteria can circumvent the action of other antibiotics for example, mupirocin is not degraded [200]. 

Fig. 4.4 Secondary structure of the PTC and antibiotic information. Nucleotide numbering is from H. marismortui (Hm) and is followed by the standard corresponding coli (Ec) numbering in parentheses. Nucleotides with superscripts have been implicated in antibiotic interactions by nucleotide protection studies (green) [54-57] or by mutations (orange) that confer resistance to carbomycin A (M) linco-samides (L) streptogramin A [58] (S) chlor-...

The possibility of errors in deposited structures must be considered. Errors in chirality may be prevalent in high resolution small molecule structures. For example, the small molecule structure of streptogramin A is represented by its enantiomer in the Cambridge Structural Data Base. The effort to solve the structure of streptogramin A bound to the ribosome was initially hindered by relying on that incorrect small molecule structure. Likewise, the structure of anisomycin is incorrectly diagrammed as its enantiomer in most of the ribosomal literature. Fortunately, these chirality errors were identified when solving structures of these antibiotics bound to macromolecules. In fact, the identification of these errors may increase confidence in the reliability of these structures of complexes between ribosomes and antibiotics. 

PoRSE, B.T., Garrett, R.A., Sites of interaction of streptogramin A and B antibiotics in the peptidyl transferase loop of 23S rRNA and the synergism of their inhibitory mechanisms. J. Mol. Biol. 1998, 286, 375-387. 

Figure 11 Chemical modification of Type B streptogramins. These antibiotics bind to the large ribosome adjacent to the chloramphenicol binding site (A). A key interaction with the 23 S rRNA is blocked by the action of VAT-dependent acetylation (B).

Sugantino M, Roderick SL. Crystal structure of Vat(D) an acetyltransferase that inactivates streptogramin group A antibiotics. Biochemistry 2002 41 2209-2216. 

Pulsawat N, Kitani S, Nihira T. Characterization of biosynthetic gene cluster for the production of virginiamycin M, a streptogramin type A antibiotic, in Streptomyces virginiae. Gene 2007 393 31-42. 

Most of the data on rokitamycin have been published in Japanese and Italian journals. As a propionyl ester of leucomycin, rokitamycin has an antimicrobial spectrum similar to that of erythromycin, it is especially potent against L. pneumophila, M. pneumoniae, and Chlamydia. Like other 16-membered macrolides, it is active against bacteria that are inducibly resistant to erythromycin but inactive against strains that are constitutively resistant to macrolide-lincosamide-streptogramin B antibiotics. 

Matsuoka, M., Endou, K., Saitoh, S., Katoh, M., and Nakajima, Y. (1995). A mechanism of resistance to partial macrolide and streptogramin B antibiotics in Staphylococcus aureus clinically isolated in Hungary. Biol. Pharm Bull. 18, 1482-1486. 

Cundliffe, E. (1969). Antibiotics and polyribosomes. II. Some effects of lincomycin, spiramycin, and streptogramin A in vivo. Biochemistry 8, 2063-2066. 

Uchiyama, H., and Weisblum, B. (1985). A-Methyl transferase of Streptomyces erythreus that confers resistance to the macrolide-lincosamide-streptogramin B antibiotics Amino acid sequence and its homology to cognate R-factor enzymes from pathogenic bacilli and cocci. Gene 38, 103-110. 

Pristinamycin is a member of the streptogramin class of antibiotics effective against vancomycin-resistant S. aureus and vancomycin-resistant enterococcus. It is biosynthesized by the bacterium Streptomyces pristinaespiralis and consists of two components, pristinamycin lA (a macro-lide) and the depsipeptide pristinamycin HA (also known as streptogramin A) in the ratio of 30 70. Streptogramins, also called synergistins, are made up of two groups, streptogramins A and B. 

Antibiotics acting on the larger ribosome subunit - The effects of specific inhibitors of peptide bond formation by either 70 S ribosomes (amicetin, sparsomycin, gougerotin and antibiotics of the chloramphenicol, macrolide, streptogramin A and lincomycin groups) or by 80 S ribosomes (amicetin, sparsomycin, gougerotin and anisomycin) have been reviewed recently . 

Another characterization of the binding of peptidyl-tRNA analogs to the ribosome is based on the response to antibiotic inhibitors of peptidyl-transferase activity. Although Oen et al. observed no inhibition of reversible binding of iV-bromoacetyl Phe-tRNA by chloramphenicol, lin-comycin, or streptogramin A, the same antibiotics as well as erythromycin significantly inhibited the binding of p-azido-A-tBoc-Phe-Phe-tRNA. It should be noted, however, that in both cases the antibiotics markedly reduced the extent of the covalent reaction of the aflSnity probes with the ribosome. 

Shaginian A, Rosen MC, Binkowski BF, Belshaw PJ. Solid-phase synthesis of dihydrovirginiamycin SI, a streptogramin B antibiotic. Chem. Eur. J. 2004 10 4334-4340. 

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