Protein Sorting and Delivery Mechanisms

The process where proteins are delivered to the correct organelles within a eukaryotic cell.

A short amino acid sequence within a protein that acts as an address label, directing the protein to the correct organelle.

The mechanism by which proteins are transported into different organelles like the nucleus, mitochondria, and peroxisomes.

Proteins are synthesized in the cytoplasm and then transported to different organelles like the nucleus, mitochondria, or ER. Signal sequences guide these proteins to their destinations.

Different signal sequences have different characteristics, like N-terminus location, hydrophobicity, basic amino acids. These features are important for targeting proteins to particular organelles.

Nuclear pores are the gateways between the nucleus and cytoplasm, allowing proteins to enter and exit in their folded state.

A specific amino acid sequence on a protein that directs it to the nucleus.

Small proteins (<40 kDa) enter the nucleus via passive diffusion through a nuclear pore's hydrogel interior.

Larger proteins or protein complexes enter the nucleus via active transport with import receptors and energy.

The Ran-GTP/GDP cycle provides directional movement during nuclear transport by changing the binding affinity of proteins to and from the nucleus.

The process of proteins entering the nucleus driven by GTP hydrolysis energy.

Proteins that recognize and bind to NLS-containing proteins, assisting their transport through nuclear pores.

Similar to nuclear import, but in reverse, proteins exit the nucleus.

Proteins enter mitochondria using a two-step process, with the TOM and TIM complexes forming a channel across the double membrane.

A protein complex in the outer mitochondrial membrane that helps proteins enter the mitochondria.

A protein complex in the inner mitochondrial membrane that helps proteins cross into the mitochondrial matrix.

Peroxisomes break down fatty acids, convert toxic substances, and synthesize lipids.

Peroxisomes bud off from the ER, and are separated from the cytosol by a membrane.

An enzyme in peroxisomes that breaks down hydrogen peroxide into harmless substances.

Mitochondrial protein import requires energy (active transport).

A short stretch of alternating hydrophobic residues that signals a protein for export from the nucleus.

NF-κB, a protein involved in the immune response, is normally inactive in the cytoplasm, bound by IκB. Infection triggers IκB degradation, releasing NF-κB, which then translocates to the nucleus to activate genes.

Usually located at the N-terminus, it's an amphipathic alpha-helix with hydrophobic residues on one side and charged basic residues on the other.

The process of moving proteins across biological membranes. Specific receptors and membrane channels are required in organelles such as mitochondria.

The N-terminus of a mitochondrial precursor protein enters first during the import process.

Soluble proteins are imported into peroxisomes in a folded state via a translocation channel. This process uses a receptor (R) that recognizes peroxisome import signals (e.g., SKL) and shuttles it into the peroxisome.

A protein that recognizes specific signals (like SKL)on proteins destined for peroxisomes and shuttles them into the organelle. The receptor is recycled back to the cytosol.

Catalase, if present in cells lacking peroxisomes, would likely be found throughout the cytoplasm (not within any specific structure).

Catalase appears as small dots in normal cells due to the fluorescent signal being localized within the peroxisomes of those cells' cytoplasm. The signal is amplified within these organelles.

Proteins destined for the endoplasmic reticulum (ER) are imported while still being synthesized on ribosomes.