protein transport

Definition

Target type: biologicalprocess

The directed movement of proteins into, out of or within a cell, or between cells, by means of some agent such as a transporter or pore. [GOC:ai]

Protein transport is the movement of proteins from their site of synthesis (ribosomes) to their final destination within the cell or outside the cell. This process is essential for cellular function, as it ensures that proteins are delivered to the correct location where they can perform their specific roles.

**There are two main pathways of protein transport:**

**1. Co-translational translocation:**
- This pathway occurs while the protein is being synthesized by ribosomes.
- Ribosomes bind to the endoplasmic reticulum (ER) membrane, and the nascent protein is directly inserted into the ER lumen.
- This process is facilitated by signal sequences within the protein that guide it to the ER and by chaperone proteins that assist in folding.

**2. Post-translational translocation:**
- This pathway occurs after protein synthesis is complete.
- Proteins are transported to their target destinations through various mechanisms, including:
- **Nuclear transport:** Proteins destined for the nucleus are transported through nuclear pores.
- **Mitochondrial transport:** Proteins targeted to mitochondria are imported through protein translocators in the mitochondrial membranes.
- **Peroxisomal transport:** Proteins destined for peroxisomes are transported through peroxisomal translocators.

**Key steps involved in protein transport:**

- **Signal recognition:** Signal sequences on the protein are recognized by specific receptors, like the signal recognition particle (SRP).
- **Targeting and docking:** The protein complex is targeted to the correct organelle or membrane and docks to a specific receptor.
- **Translocation:** The protein is translocated across the membrane, often with the help of chaperones and protein translocators.
- **Folding and modification:** Once inside the target compartment, the protein undergoes proper folding and may be modified through glycosylation, phosphorylation, or other processes.
- **Quality control:** There are mechanisms in place to ensure that misfolded or improperly transported proteins are degraded or refolded.

**Protein transport is a highly regulated process that ensures:**

- Correct protein localization: Proteins are delivered to the appropriate compartments within the cell, where they can perform their specific functions.
- Efficient protein function: Properly folded and localized proteins can interact with other molecules and carry out their assigned tasks effectively.
- Cellular homeostasis: Protein transport contributes to maintaining the balance and proper functioning of cellular processes.

Protein transport plays a crucial role in various cellular functions, including:

- Synthesis and secretion of hormones, enzymes, and other proteins
- Building and maintaining cellular structures
- Transporting nutrients and waste products
- Regulating cellular processes such as signal transduction and gene expression'
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Proteins (21)

Compounds (250)