# Inhibitors, drugs, toxins
###### tags: `共筆`
## Transcription inhibitor
* **Rifampicin** and **Streptolydigin**
> RNA polymerase β subunit
* **α-amanitin** (low conc)
> RNA polymerase II
* α-amanitin (high conc)
> RNA polymerase III
* Cordyceptin (3'-deoxyadenosine)
> Transcription chain terminator
> both prokaryotesand eukaryotes
* Actinomycin D & Acridine
> intercalation into DNA between two GC base pairs -> prevents polymerase movement
> both prokaryotesand eukaryotes
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## Translation inhibitor
* Chloramphenicol
> Bind to 50s
> Prevents peptide bond formation
* **Erythromycin**
> Bind to 50s
> Prevents translocation
* **Tetracyclines**
> Binds to 30s
> Prevents tRNA binding to A site
> Also works in eukaryotes
* Strepromycin
> Binds to 30s
> Alter the structure of 30s
* **Puromycin**
> Like aminoacyl-tRNA
> Terminate the protein synthase
> Also works in eukaryotes
* Cycloheximide
> Inhibits the translocation activity in the eukaryotic ribosome
* **Diphtheria toxin**
> Inactivated eEF2 (by ++ADP-ribosylation++ on histone)
## Nucleus receptor targeting drugs
### Agonists
* Pharmacological glucocorticoids
> Cortisolm, Triamicinolone, Prednisone, Dexamethasone
> -> transcription of IκBα -> binds to NF-κB -> ubiquitination
### Antagonists
* Tamoxifen
> Breast tumor treatment
> Binds to estrogen receptors
* RU486
> Contraceptive agent (避孕藥)
> Binds to progesterone receptors
## Nicotinic acetylcholine receptor agonists/antagonists
* Sarin
> Irreversibly inactivating AChE (Acetylcholinesterase) -> 造成ACh過度影響ion channel
> Causes paralysis
* Tubocurarine
> Blocks the channel (Receptor antagonist)
## Guanylyl cyclases
* Sildenafil (威爾鋼)
> Inhibit cGMP phosphodiesterase -> cGMP ↑ -> Longer vasodilation
* Bacterial endotoxin
> Guanylin -> severe diarrhea.
## G protein
* Cholera toxin (CT)
> ++ADP-ribosylation++ of Gsα -> GTPase activity inhibited -> Gs locked in an active -> Adenylate cyclase ↑ -> cAMP ↑
* Pertussis toxin (PT)
> ++ADP-ribosylation++ of Giα -> no GDP-to-GTP nucleotide exchange -> Gi locked in an inactive -> Adenylate cyclase ↑ -> cAMP ↑
## Phosphatidylinositol-derived second messengers
* Phorbol esters
> Like DAG
> Tumor promoters