Inhibition of Ribosomal A Site Functions by Sporangiomycin and Micrococcin

Abstract

Sporangiomycin and micrococcin inhibit the binding of aminoacyl-transfer ribonucleic acid into the ribosomal A site in intact bacterial protoplasts. They also prevent the assembly of [ribosome-elongation factor G-guanine nucleotide] complexes in vitro and compete with [(35)S]thiostrepton for ribosomal binding sites. We conclude that micrococcin and sporangiomycin block the ribosomal A site in the vicinity of the complex guanosine triphosphatase center and so resemble thiostrepton in their modes of action.

YcaO-Dependent Posttranslational Amide Activation: Biosynthesis, Structure, and Function

“…444–450 Consequently, the binding of thiopeptides with a 26-member macrocycle in this area can affect all phases of translation, 451–458 but the most studied effects are on EF-Tu and EF-G during elongation. 458–474 Inhibition of EF-Tu and tRNA delivery presumably occurs because thiopeptides partially conflict with the ternary (EF-Tu, GTP, and aminoacyl-tRNA) complex’s binding site near the 23S rRNA/L11. 447, 448, 473 In contrast, the mechanism of action against EF-G varies depending on the thiopeptide.…”

“…In contrast, thiopeptides with 26-membered macrocycles (e.g., thiostrepton, siomycin, nosiheptide, berninamycin, and thiocillin/micrococcin) target the 50S subunit of by interacting with the 23S rRNA and ribosomal protein L11. ,,− Binding is mediated primarily by interaction with 23S rRNA and is cooperative with L11. − Resistance to thiopeptides of this variety occurs through mutation of either 23S rRNA or L11. ,− Alternatively, methylation of the 23S rRNA also confers resistance. − Improving initial models, , more recent structural studies based on NMR, X-ray crystallography, and molecular modeling showed that these 26-membered thiopeptides bind to a cleft between the 23S rRNA and L11, ,− but covalent capture data suggest binding may be more on the surface of the rRNA and not between 23S/L11 . The interface of the 23S rRNA and L11 is called the “GTPase-associated center” and is crucial for ribosome function given its interaction with many translation factors. − Consequently, the binding of thiopeptides with a 26-member macrocycle in this area can affect all phases of translation, − but the most studied effects are on EF-Tu and EF-G during elongation. − Inhibition of EF-Tu and tRNA delivery presumab...…”

“…The interface of the 23S rRNA and L11 is called the “GTPase-associated center” and is crucial for ribosome function given its interaction with many translation factors. − Consequently, the binding of thiopeptides with a 26-member macrocycle in this area can affect all phases of translation, − but the most studied effects are on EF-Tu and EF-G during elongation. − Inhibition of EF-Tu and tRNA delivery presumably occurs because thiopeptides partially conflict with the ternary (EF-Tu, GTP, and aminoacyl-tRNA) complex’s binding site near the 23S rRNA/L11. ,, In contrast, the mechanism of action against EF-G varies depending on the thiopeptide. Specifically, thiopeptides with a secondary quinaldic/indolic ring (i.e., thiostrepton/nosiheptide) interact differently with EF-G than those that have just one macrocycle (i.e., micrococcin) because they bind in slightly different orientations at the 23S rRNA/L11 interface. ,,, Thiostrepton disrupts binding of EF-G to the ribosome, thereby inhibiting GTP hydrolysis, ,− ,, and stabilizes a conformation of 23S rRNA/L11 that prevents the structural transitions necessary for translocation. ,,, This means that even with transient EF-G binding, as suggested by some studies of thiostrepton-bound ribosomes, − translation remains arrested. Conversely, micrococcin enhances EF-G GTPase activity without effecting its binding affinity and blocks the translocation process through a similar rigidifying and restriction of 23S rRNA/L11. ,,, …”

Bacteriocins of gram-positive bacteria.

“…strain NCTC 7218 produces an antibiotic, micrococcin (73, 268), which is a peptide of molecular weight 2,000 (115), mainly active on gram-positive bacteria (267), and insensitive to trypsin (267). Recent studies indicate that micrococcin may act by blocking the binding of aminoacyl-transfer ribonucleic acid to the ribosomal A site (47).…”

Domain Reorientation and Induced Fit upon RNA Binding: Solution Structure and Dynamics of Ribosomal Protein L11 from Thermotoga maritima

“…[8,9] The L11-RNA complex is a target of the thiazole family of antibiotics that includes thiostrepton and micrococcin. [10][11][12] These antibiotics inhibit ribosome function by interfering with the interaction of EF-G and EF-Tu-aminoacyl-tRNA-GTP (EFTu-aa-tRNA-GTP) complex with the large 50S ribosomal subunit. The affinity of thiostrepton for the 23S rRNA domain is greatly increased in the presence of full-length L11 but not with the C-terminal domain alone.…”