Post-translational modification | co translational translocation | Signal Recognition Particle SRP

Summary

This transcript explains the process by which proteins are synthesized and modified in the endoplasmic reticulum (ER). It details how translation begins with the synthesis of a signal peptide, which is recognized by a signal recognition particle (SRP). The SRP then binds to a receptor in the ER membrane, anchoring the ribosome. As translation continues, the protein passes through the translocator, where the signal peptide is cleaved, leaving the newly synthesized protein in the ER lumen for further modifications such as sugar addition.

Takeaways

• 😀 Proteins enter the endoplasmic reticulum (ER) for sugar modification during translation.
• 😀 Translation begins with the synthesis of a short signal peptide sequence.
• 😀 The signal recognition particle (SRP) binds to the signal peptide during translation.
• 😀 The SRP directs the ribosome to the ER membrane by binding to its receptor.
• 😀 The ribosome anchors to the ER membrane through the SRP-receptor interaction.
• 😀 The signal peptide interacts with the protein translocator in the ER membrane.
• 😀 Translation continues as the protein chain is threaded through the translocator.
• 😀 The protein passes into the lumen of the ER for further processing.
• 😀 The signal peptide is cleaved off by signal peptidase after the protein enters the ER.
• 😀 The final protein is left in the lumen of the ER for modification and folding.

Q & A

What is the main purpose of proteins entering the endoplasmic reticulum (ER)?

Proteins enter the ER for modification with sugars, which is essential for their proper folding and function.

What is the first step in the process of a protein entering the ER?

The process begins with the synthesis of a short signal peptide sequence during translation.

What role does the signal recognition particle (SRP) play in protein translocation to the ER?

The SRP binds to the signal peptide while translation continues, guiding the ribosome to the ER membrane.

How does the SRP contribute to ribosome anchoring at the ER?

The SRP binds to its receptor in the ER membrane, anchoring the ribosome in place for further protein synthesis and translocation.

What happens after the ribosome is anchored at the ER membrane?

The ribosome binds to its receptor, and the signal peptide interacts with the protein translocator, allowing translation to proceed.

What is the function of the protein translocator in this process?

The protein translocator facilitates the passage of the nascent protein into the ER lumen as translation continues.

What role does the signal peptidase play in protein translocation?

The signal peptidase cleaves the signal peptide after the protein enters the ER lumen, leaving the newly synthesized protein in the ER.

Where is the newly synthesized protein located after the signal peptide is cleaved?

After the signal peptide is cleaved, the new protein molecule is left in the lumen of the endoplasmic reticulum.

How does the process described contribute to protein maturation?

This process ensures that proteins are properly modified, including sugar additions, which are crucial for their correct folding and eventual function.

Why is the signal peptide important in the process of protein translocation?

The signal peptide directs the ribosome to the ER membrane, where the protein is translocated into the lumen for further processing.