Question

RECALL How does puromycin function as an inhibitor of protein synthesis?

Short answer

Puromycin causes premature chain termination during translation by mimicking aminoacyl-tRNA and releasing the peptide chain early, resulting in incomplete proteins.

Step-by-step solution

- Identify the Role of Puromycin

Understand that puromycin is an antibiotic that affects protein synthesis in cells.

- Understand Protein Synthesis

Protein synthesis involves the translation of mRNA into polypeptides on ribosomes.

- Mechanism of Action

Explain that puromycin causes premature chain termination during translation. It resembles the 3' end of aminoacyl-tRNA, thereby entering the A site of the ribosome.

- Inhibition Process

Detail how puromycin binds to the growing peptide chain and causes it to be released prematurely, inhibiting further elongation of the peptide.

- Result of Inhibition

Describe that this leads to incomplete, non-functional proteins being produced, thereby halting effective protein synthesis.

Key concepts

Puromycin Inhibition of Protein Synthesis

Puromycin is a fascinating antibiotic specifically known for its impact on protein synthesis within cells. But how does it achieve this? Protein synthesis is a crucial process where mRNA is translated into polypeptides, essential for various cellular functions.
Puromycin intervenes in this process by mimicking the 3' end of aminoacyl-tRNA, which is a structure that normally fits into the ribosome during translation. Once puromycin enters the ribosome's A site, it integrates into the growing peptide chain. However, unlike the usual aminoacyl-tRNA, puromycin causes premature termination of the peptide chain, leading to incomplete and non-functional proteins.
This premature termination effectively halts further elongation of the peptide and thus inhibits protein synthesis altogether.

Protein Synthesis

Protein synthesis is a fundamental biological process. It translates genetic information from mRNA into functional proteins.
The process occurs in two main stages:

• Transcription, where DNA is copied into mRNA.
• Translation, where ribosomes use mRNA to build polypeptides.

In translation, ribosomes read the mRNA sequence and assemble amino acids in the correct order to form a specific protein. This is essential for cell function, growth, and repair. Ribosomes facilitate this by moving along the mRNA strand and sequentially adding amino acids brought by aminoacyl-tRNA.

Antibiotics

Antibiotics are compounds used to inhibit the growth of or kill bacteria. They achieve this by targeting specific bacterial processes.
For example, puromycin targets protein synthesis, a vital process in bacteria. By disrupting protein synthesis, antibiotics like puromycin can prevent bacteria from producing essential proteins, ultimately stopping them from growing or causing harm.

Translation Mechanism

The translation mechanism is key to understanding how genetic information becomes functional proteins. This multi-step process occurs mainly in ribosomes. Here's a simplified breakdown:

• Initiation: Ribosome assembles around the mRNA to be read.
• Elongation: Ribosome travels along the mRNA, and tRNA molecules bring amino acids to build the polypeptide chain.
• Termination: When a stop codon is reached, the ribosome releases the complete polypeptide.

In the elongation phase, aminoacyl-tRNA delivers specific amino acids, which the ribosome links into a growing polypeptide chain.

Ribosome Function

Ribosomes are cellular structures that play a critical role in protein synthesis. They consist of ribosomal RNA (rRNA) and proteins. Ribosomes read the mRNA sequence, and with the help of tRNA, they assemble amino acids in the correct sequence to form proteins.
There are two main sites in the ribosome essential for translation:

• A site: Where aminoacyl-tRNA enters the ribosome.
• P site: Where the growing polypeptide chain is held.

Each time an amino acid is added, the ribosome shifts, allowing the next aminoacyl-tRNA to enter the A site. If an inhibitor like puromycin enters, it disrupts this process by causing early termination.

Aminoacyl-tRNA

Aminoacyl-tRNA is a key player in protein synthesis. It consists of a transfer RNA (tRNA) attached to an amino acid. This molecule plays a pivotal role in translating genetic information into proteins.
Here's how it works:

• Aminoacyl-tRNA synthetase enzymes attach the correct amino acid to its corresponding tRNA.
• The aminoacyl-tRNA then transports the amino acid to the ribosome, where the mRNA sequence is being read.
• As the ribosome reads the codons in the mRNA, the corresponding aminoacyl-tRNA binds, adding its amino acid to the growing polypeptide chain.

Proper function of aminoacyl-tRNAs is crucial for accurate protein synthesis and cellular function.