Question

Tetracycline binds to the

• A. 30S subunit and inhibits aminoacyl-tRNA binding
• B. 50S subunit and inhibits aminoacyl-tRNA binding
• C. 30S subunit and prevents codon:anticodon interactions
• D. 50S subunit and blocks exit of growing polypeptide chain

Answer 1

The Correct Option is A

The question asks about the mechanism of action of tetracycline, an antibiotic. To solve this, let's examine how tetracycline affects bacterial cells.

Tetracycline is known to specifically target the ribosomal machinery in bacteria, which is crucial for protein synthesis. Here’s how it works:

1. Bacterial Ribosome Structure: Bacterial ribosomes are composed of two subunits: the smaller 30S subunit and the larger 50S subunit. Together, they function to translate mRNA sequences into proteins.
2. Mechanism of Tetracycline: Tetracycline binds to the 30S subunit of the bacterial ribosome. This binding interferes with the attachment of aminoacyl-tRNA to the mRNA-ribosome complex. Without aminoacyl-tRNA, the ribosome cannot add new amino acids to the growing polypeptide chain, thereby inhibiting protein synthesis.

Based on the above details, let's evaluate the provided options:

• Option 1:
  30S subunit and inhibits aminoacyl-tRNA binding
  
  This is true as tetracycline binds to the 30S ribosomal subunit and blocks the binding of aminoacyl-tRNA, halting protein synthesis.
• Option 2:
  50S subunit and inhibits aminoacyl-tRNA binding
  
  This is incorrect. Tetracycline does not interact with the 50S subunit; its action is specific to the 30S subunit.
• Option 3:
  30S subunit and prevents codon:anticodon interactions
  
  This is inaccurate because tetracycline does not prevent codon:anticodon interaction; it specifically prevents aminoacyl-tRNA from binding.
• Option 4:
  50S subunit and blocks exit of growing polypeptide chain
  
  This is not applicable to tetracycline as it does not bind or affect the 50S subunit.

Conclusion: The correct answer is that tetracycline binds to the 30S subunit and inhibits aminoacyl-tRNA binding, effectively stopping protein synthesis in bacteria.