protein transmembrane import into intracellular organelle

Definition

Target type: biologicalprocess

The directed movement of proteins into an intracellular organelle, across a membrane. [GOC:jl]

Protein transmembrane import into intracellular organelles is a fundamental process in cellular biology, ensuring the proper localization and function of proteins within different compartments. This intricate process involves a series of steps, starting with the synthesis of the protein on ribosomes and culminating in its delivery to the target organelle.

Here's a detailed description:

1. **Signal Peptide Recognition:** The journey begins with the synthesis of a protein destined for an organelle. Such proteins typically possess a signal peptide, a short amino acid sequence at the N-terminus that acts as a "zip code," directing the protein to its correct destination. The signal peptide interacts with a signal recognition particle (SRP), a cytosolic ribonucleoprotein complex.

2. **SRP-Ribosome Binding and Targeting to the Translocon:** The SRP, carrying the ribosome-bound nascent polypeptide, interacts with the SRP receptor on the organelle's membrane. This interaction triggers the recruitment of the ribosome to the translocon, a protein channel embedded in the membrane.

3. **Translocation through the Translocon:** Once docked at the translocon, the nascent polypeptide begins its journey across the membrane. The signal peptide enters the translocon first, followed by the rest of the polypeptide chain. The translocon acts as a gatekeeper, allowing passage only to the target protein.

4. **Signal Peptide Cleavage:** As the protein translocates, the signal peptide is often cleaved off by a signal peptidase enzyme located in the organelle lumen. This cleavage event is crucial for the proper folding and function of the protein within the target compartment.

5. **Folding and Chaperone Assistance:** Once inside the organelle, the translocated protein folds into its native three-dimensional structure. This process can be aided by chaperone proteins, which prevent misfolding and aggregation.

6. **Organelle-Specific Sorting:** Some proteins destined for specific intracellular organelles, such as the Golgi apparatus or the endoplasmic reticulum, might require additional sorting signals or chaperone interactions to ensure their proper delivery.

7. **Post-Translational Modifications:** Many proteins undergo post-translational modifications, such as glycosylation or phosphorylation, after reaching their destination, which further contribute to their function and stability.

In summary, protein transmembrane import is a complex process that involves a series of well-coordinated steps, ensuring the efficient and precise delivery of proteins to their appropriate intracellular locations, ultimately contributing to the proper functioning of the cell.'
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Proteins (1)

Compounds (9)