Question

Describe the steps that occur between the time a ribosome attaches to a messenger RNA encoding a secretory protein and the time the protein leaves the Rough Endoplasmic reticulum (RER).

Answer 1

The steps between ribosome attachment to mRNA encoding a secretory protein and protein release from the RER involve SRP binding and interaction with the RER membrane.

Step-by-step explanation:

The steps that occur between the time a ribosome attaches to a messenger RNA encoding a secretory protein and the time the protein leaves the Rough Endoplasmic Reticulum (RER) are as follows:

1. An SRP (signal recognition particle) binds to the hydrophobic signal peptide.
2. Elongation stops until the SRP-ribosome complex finds the RER membrane.
3. The ribosome-SRP complex binds to an SRP receptor on the RER membrane.

After the ribosome attaches to the mRNA, the SRP binds to the signal peptide of the secretory protein. This binding pauses elongation until the SRP-ribosome complex reaches the RER membrane. Once there, the complex binds to an SRP receptor on the membrane, allowing the protein to continue its synthesis and eventual release from the RER.