The protein synthesis inhibitor thermorubin. 2. Mechanism of inhibition of initiation on Escherichia coli ribosomes

Lin, Fwu Lai; Wishnia, Arnold

doi:10.1021/bi00532a011

Cited by 10 publications

(15 citation statements)

References 36 publications

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“…Thermorubin has relatively little effect on in vitro poly(U) dependent poly-phenylalanine synthesis, a process that bypasses the normal route of translation initiation 6; 9 , whereas thermorubin effectively inhibits the in vitro translation of an endogenous mRNA containing a start codon and Shine-Dalgarno sequence 6 . While poly(U) dependent poly-phenylalanine synthesis is not inhibited by thermorubin under physiological magnesium concentrations (6mM), the drug is able to block poly-phenylalanine synthesis under elevated magnesium concentrations (12mM) 9 . Interestingly, the level of inhibition that can be achieved depends on whether thermorubin is introduced before or after poly(U) is added to the system.…”

Section: Discussionmentioning

confidence: 99%

“…It has also been observed that thermorubin is able to prevent initiator tRNA from binding to the E.coli ribosome when initiation factors are present 9 . The region of the ribosome at which thermorubin binds, inter-subunit bridge B2a (Figure 2a), has been shown to play a role in factordependent translation initiation 17; 18 and IF1 and IF2 have been observed to make contacts with this region 19; 20; 21; 22 .…”

Section: Discussionmentioning

confidence: 99%

“…The first is that thermorubin prevents dissociation of the 70S ribosome into subunits 15 . Second, thermorubin inhibits protein synthesis at higher magnesium concentrations (above 12 mM) 9 , suggesting that the combined stabilizing effects of high magnesium and thermorubin cooperatively block translation by limiting inter-subunit mobility.…”

Section: Discussionmentioning

confidence: 99%

“…Thermorubin is able to inhibit protein synthesis, but only under certain conditions. First, it does not inhibit poly(U)-directed poly(Phe) synthesis at low magnesium concentrations (5mM) or in the absence of initiation factors 6 , nor does it affect the reactivity of puromycin with the 70S ribosome complex with AcPhe-tRNA and poly(U) 9 . However, when initiation factors are also present, thermorubin inhibits both poly(U)-directed poly(Phe) synthesis and the binding of fMet-tRNA to the 70S ribosome 6 .…”

Section: Introductionmentioning

confidence: 99%

“…However, when initiation factors are also present, thermorubin inhibits both poly(U)-directed poly(Phe) synthesis and the binding of fMet-tRNA to the 70S ribosome 6 . Interestingly, it is also able to block poly(U)-directed poly(Phe) synthesis when the magnesium concentration is raised to 12 mM 9 . Finally, thermorubin promotes subunit association at magnesium concentrations that ordinarily promote subunit dissociation 8 .…”

Section: Introductionmentioning

confidence: 99%

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The Antibiotic Thermorubin Inhibits Protein Synthesis by Binding to Inter-Subunit Bridge B2a of the Ribosome

Bulkley

Johnson

Steitz

2012

Journal of Molecular Biology

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Thermorubin is a small molecule inhibitor of bacterial protein synthesis, but relatively little is known about the molecular mechanism by which it blocks translation. The structure of the complex between thermorubin and the 70S ribosome from Thermus thermophilus reported here shows that thermorubin interacts with the ribosome in a way that is distinct from any other known class of ribosome inhibitor. Though it is structurally similar to tetracycline, it binds to the ribosome at an entirely different location - the interface between the small and large subunits that is formed by intersubunit bridge B2a. This region of the ribosome is known to play a role in the initiation of translation, and thus the binding site we observe is consistent with evidence suggesting that thermorubin inhibits the initiation stage of protein synthesis. The binding of thermorubin induces a rearrangement of two bases on helix 69 of the 23S rRNA and presumably this rearrangement blocks the binding of an A-site tRNA, thereby inhibiting peptide bond formation. Due in part to its low solubility in aqueous media, thermorubin has not been used clinically, although it is a potent antibacterial agent with low toxicity (Theraputic Index > 200). The interactions between thermorubin and the ribosome, as well as its adjacency to the observed binding sites of three other antibiotic classes, may enable the design of novel derivatives that share thermorubin’s mode of action but possess improved pharmacodynamic properties.

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