Protein Sorting and Translocation Mechanisms

This set of flashcards covers key vocabulary and concepts related to protein sorting and translocation mechanisms, including various transport processes, protein modifications, and the roles of specific proteins and enzymes involved in these processes.

Cotranslational translocation

The process where many cell proteins pass through the ER during their synthesis.

Signal sequence

A peptide sequence that directs proteins to the ER and is cleaved by signal peptidase.

Signal recognition particle (SRP)

A protein-RNA complex that recognizes and targets the signal sequence to the ER membrane.

Sec61 protein translocator

A protein complex that forms an aqueous pore in the ER membrane for translocating polypeptides.

Posttranslational translocation

A mechanism where proteins synthesized by free ribosomes are translocated to the ER lumen after synthesis.

Glycosylation

The process of adding oligosaccharides to a protein, aiding in proper folding and stability.

Transmembrane transport

Transport mechanism for proteins moving through membranes of organelles such as mitochondria and the ER.

Vesicular transport

The process of moving proteins in vesicles along the secretory pathway.

Gated transport

Transport mechanism that controls the movement of proteins into and out of the nucleus.

Internal signal sequence

A sequence that initiates translocation for single-pass transmembrane proteins.

Misfolded proteins

Proteins that fail to fold properly and are targeted for degradation.

Molecular chaperones

Proteins that assist in the folding and assembly of other proteins.

Peptidase

An enzyme that cleaves peptide bonds in proteins.

Calnexin

A molecular chaperone that binds to incompletely folded proteins in the ER.

Glucosidase

An enzyme that trims glucose residues during the protein folding process.

Ubiquitination

The process of marking proteins for degradation by attaching ubiquitin.

Translocon

A protein complex that facilitates the passage of polypeptides into the ER.

Stop-transfer signal

A sequence that halts translocation, allowing the protein to embed in the membrane.

Signal peptidase

An enzyme that removes signal sequences from polypeptides after translocation.