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Antibiotics and Protein Synthesis
Antibiotics are molecules produced by microorganisms as defense mechanisms. The most effective antibiotics work by interfering with essential biochemical or reproductive processes. Many antibiotics block or disrupt one or more stages in protein synthesis. Some of these are mentioned here.
Tetracyclines are a family of chemically related compounds used to treat several types of bacterial infections. Tetracyclines interfere with the initiation of translation. The tetracycline molecule attaches to the small ribosomal subunit and prevents binding of the tRNA anticodon during initiation. Both eukaryotic and prokaryotic ribosomes are sensitive to the action of tetracycline, but this antibiotic cannot pass through the plasma membrane of eukaryotic cells. Because tetracycline can enter bacterial cells to inhibit protein synthesis, it will stop bacterial growth, helping the immune system fight the infection.
Streptomycin is used in hospitals to treat serious bacterial infections. It binds to the small ribosomal subunit but does not prevent initiation or elongation; however, it does affect the efficiency of protein synthesis. Binding of streptomycin changes the way mRNA codons interact with the tRNA. As a result, incorrect amino acids are incorporated into the growing polypeptide chain, producing nonfunctional proteins. In addition, streptomycin causes the ribosome to randomly fall off the mRNA, preventing the synthesis of complete proteins.
Puromycin is not used clinically but has played an important role in studying the mechanism of protein synthesis in the research laboratory. The puromycin molecule is the same size and shape as a tRNA/amino acid complex. When puromycin enters the ribosome, it can be incorporated into a growing polypeptide chain, stopping further synthesis because no peptide bond can be formed between puromycin and an amino acid, causing the shortened polypeptide to fall off the ribosome.
Chloramphenicol was one of the first broadspectrum antibiotics introduced. Eukaryotic cells are resistant to its actions, and it was widely used to treat bacterial infections. However, its use is limited to external applications and serious infections. Chloramphenicol destroys cells in the bone marrow, the source of all blood cells. In bacteria, this antibiotic binds to the large ribosomal subunit and inhibits the formation of peptide bonds. Another antibiotic, erythromycin, also binds to the large ribosomal subunit and inhibits the movement of ribosomes along the mRNA.
Almost every step of protein synthesis can be inhibited by one antibiotic or another. Work on designing new synthetic antibiotics to fight infections is based on our knowledge of how the
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Why are antibiotics ineffective in treating the common cold and other virus infections?
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Chapter 9 Solutions
Human Heredity: Principles and Issues (MindTap Course List)
- Many antibiotics are effective as drugs to fight off bacterial infections because they inhibit protein synthesis in bacterial cells. Using the information provided in the following table that highlights several antibiotics and their mode of action, discuss which phase of translation is inhibited: initiation, elongation, or termination. What other components of the translational machinery could be targeted to inhibit bacterial protein synthesis? Antibiotic Action 1. Streptomycin Binds to 30S ribosomal subunit 2. Chloramphenicol Inhibits peptidyl transferase of 70S ribosome 3. Tetracycline Inhibits binding of charged tRNA to the A site of the ribosome 4. Erythromycin Binds to free 50S particle and prevents formation of 70S ribosome 5. Kasugamycin Inhibits binding of tRNAfMet 6. Thiostrepton Prevents translocation by inhibiting EF-Garrow_forwardBelow is a picture of a ribosome. Name and give a function of all the “players” of translation found in the picture. Explain what happens during the following steps of translation: Initiation: Elongation: Termination:arrow_forwardIdentify whether each of the following descriptions applies to typical prokaryotic genomes only, typical eukaryotic genomes only, both, or neither, according to lecture. Answer options may be used more than once or not at all. Composed of double-stranded DNA only. Each chromosome has a centromere. Species with larger genomes have more genes. [Choose ] [Choose ] prokaryotes only neither eukaryotes or prokaryotes eukaryotes only both prokaryotes and eukaryotes [Choose ]arrow_forward
- A __________ molecule is characterized by having a peptide-binding site, a modified 5’ guanine, and an anticodon. _____________ molecules are encoded by multiple gene copies in both prokaryotes and eukaryotes, and they catalyze critical reactions functions during translation. Group of answer choices mRNA; rRNA rNA; aminoacyl tRNA synthase tRNA; rRNA rRNA; precursor RNA mRNA; tRNAarrow_forwardIndicate the class of drug that is stopping polypeptide translation: change 30S subunit block ribosome attachment inhibits peptide bonding block ribosome movement block tRNA dockingarrow_forwardPosttranslational modifications of proteins do not include: peptide bond formation glycosylation acetylation of N-terminal peptide bond cleavage disulfide bond formation QUESTION 16 14 15 16 streptomycin puromycin 17 18 19 20 Which one of the following antibiotics does NOT function by interfering with the translational/post-translation process tunicamycin penicillin O tetracyclin O Oarrow_forward
- Which of the following statements about translation is false? In eukaryotes, the 5' cap and the 3' poly(A) tail are involved in translation initiation. Peptidyl-transferase activity during translation is the property of a ribozyme. A base at the first position of an anticodon on the tRNA would pair with a base at the third position of the mRNA. The growing peptide chain is transferred from the tRNA in the P site to the tRNA in the A site. Ribosomes move along an mRNA in the 3’ → 5' direction.arrow_forwardChanging only the R-group on a penicillin-family antibiotic could have many consequences. Which of the following possibilities is LEAST likely? Changing the R-group on a penicillin-family antibiotic would cause it to become a protein-synthesis inhibitor. Changing the R-group on a penicillin-family antibiotic would increase the half-life of the drug. Changing the R-group on a penicillin-family antibiotic would make a version that is more effective at killing Gram negative cells. Changing the R-group on a penicillin-family antibiotic would change the dosage that you would give a patient.arrow_forwardPolypeptides can be reversed back to RNA because of the enzyme transcriptase. The genetic material must be replicated with high fidelity and great speed. Eukaryotic mRNA is said to be polycistronic since they encode multiple polypeptide chains RNA-synthesis occurs inside the nucleus while protein synthesis in the cytoplasm of eukaryotic organisms. Write T if the statement is true and write F if the statement is falsearrow_forward
- An RNA polymer is made by using the enzyme polynucleotide phosphorylase with equal quantities of CTP and GTP. When this RNA is used in an in vitro translation system, all of the following amino acids could be incorporated into a newly made polypeptide, except: glycine (Gly) histidine (His) proline (pro) alanine (Ala) arginine (Arg)arrow_forwardWhich of the following is true about transfer RNA during translation? -Transfer RNA has anticodons that match with mRNA codons -Transfer RNA carries small ribosome subunits - Transfer RNA carries fully-functioning proteins at the end of translation -Transfer RNA carries ATP for energy during translationarrow_forwardDescribe the process of RNA interference (RNAI). Include the proteins involved, how the process works, what function(s) it performs and how RNAI might be used in basic research. Small pieces on RNA shut down protein translations. They bind to the mRNAs that code for those proteins. 1.arrow_forward
Human Heredity: Principles and Issues (MindTap Co...BiologyISBN:9781305251052Author:Michael CummingsPublisher:Cengage Learning