Antibiotics block bacterial protein synthesis
Product Manager：Harrison Michael
During protein synthesis in bacteria, antibiotics interfere with ribosome function through specific mechanisms, thereby blocking this crucial step in life activity.
I. Mechanism of action of antibiotics
1. Interference of ribosomal subunits:
Most antibiotics block protein synthesis by interfering with the 30S subunit or 50S subunit of the bacterial 70S ribosome. It is important to note that aminoacyl-trna synthetases for each amino acid required for activation peptide synthesis are not major targets of antibiotics.
2. Critical step of the attack:
Antibiotics mainly attack the following steps:
(1) Formation of 30S initiation complex, which consists of mRNA, 30S ribosomal subunit, and formyl-formthionyl transfer RNA.
(2) 30S initiation complex binds to 50S ribosome to form 70S ribosome.
(3) The elongation process of assembling amino acids into polypeptides.
3. Tetra+ antibiotics:
Tetra+ type antibiotics, including doxycycline, prevent aminoacyl-trna binding by blocking the A(aminoacyl) site of the 30S ribosome. Tetra+ antibiotics inhibit protein synthesis in 70S and 80S ribosomes, but they bind preferentially to bacterial ribosomes because of structural differences between bacterial and eukaryotic RNA subunits. In addition, Tetra+ is effective against bacteria by harnessing the bacterial transport system to allow the intracellular concentration of antibiotics to be significantly higher than the ambient concentration.
4. Aminoglycoside antibiotics:
This class of antibiotics has an affinity for the 30S ribosomal subunit. Streptomycin, as one of the most commonly used aminoglycosides, can interfere with the formation of 30S initiation complex. K+ and tobra+ also prevent the formation of larger 70S initiation complexes by binding to the 30S ribosome.
5. Macrolides:
Ery+ is a macrolide that binds to the 23S rRNA component of the 50S ribosome and interferes with the assembly of the 50S subunit. Ery+, roxithromycin, and cla+ all prevent elongation of the synthetic transpeptideization step by blocking the 50S polypeptide exit tunnel, resulting in premature termination of elongation after small peptide formation and inability to pass the macrolide barrier.
6. Peptidyl transferase inhibitors:
Peptidyl transferase is the key enzyme involved in translocation, which is the last step in the peptide elongation cycle. In contrast to lincomycin and clindamycin, which are specific inhibitors of peptidyl transferase, macrolides do not directly inhibit peptidyl transferase.
7. Puromycin:
Instead of inhibiting the enzymatic process, puromycin competes as a 3' -terminal analogue of aminoacyl-trna, interfering with synthesis and leading to premature termination of peptide chain synthesis.
8. Hygromycin B:
Hygromycin B is an aminoglycoside that binds specifically to a single site within the 30S subunit of the A, P, and E site regions of tRNA. It has been theorized that this binding may deform the ribosomal A site, which induces aminoacyl-trna misreading and a translocation that prevents peptide elongation.
II. Applications in biological experiments
1. Antibiotic susceptibility testing:
By measuring the minimum inhibitory concentration (MIC) of different antibiotics to specific bacteria, the sensitivity of bacteria to antibiotics can be assessed.
2. Drug resistance mechanism research:
Through gene mutation and phenotypic analysis, we study how bacteria develop drug resistance by changing the structure or function of the ribosome.
3. New drug development:
Understanding the mechanism of action of antibiotics helps to design new antibiotics to overcome the existing resistance problem.
4. Experimental steps:
o Bacterial culture: The target bacteria were grown in a suitable medium.
o Antibiotic treatment: Bacteria were exposed to different concentrations of antibiotics.
o Develop curve analysis: Bacterial develop in the presence of antibiotics was monitored.
o MIC determination: MIC values were determined by dilution or AGAR diffusion.
o Molecular biological analysis: PCR, sequencing and other technologies were used to analyze the genetic variation of drug-resistant strains.
5. Research fields:
The research on the mechanism of action of antibiotics involves microbiology, molecular biology, pharmacology and medicinal chemistry.
6. Application prospects:
A deeper understanding of how antibiotics inhibit bacterial protein synthesis is of great significance for the development of new antibiotics, the improvement of the use strategy of existing antibiotics, and the response to the growing problem of drug resistance.
Through these studies, the mechanism of action of antibiotics can be better understood, which can provide a theoretical basis for the development of new antibiotics and improved treatment methods. At the same time, such knowledge could also facilitate the more effective use of antibiotics in biological experiments to study the physiological and genetic properties of bacteria.
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