Cell Biology - Endoplasmic Reticulum II

These flashcards cover key concepts related to the mechanisms of protein import and translocation into the endoplasmic reticulum as discussed in the lecture.

Signal Hypothesis

The explanation for how a signal sequence in the growing polypeptide directs translation to the ER membrane.

Signal Peptide

A short peptide that directs the nascent polypeptide to the endoplasmic reticulum for translocation.

Signal Recognition Particle (SRP)

A ribonucleoprotein that binds to the signal peptide and the elongation factor binding site to pause translation and facilitate docking at the ER membrane.

Elongation Factors (EFs)

Proteins such as EF-Tu and EF-G that assist in mRNA translation by proofreading and coupling the energy of GTP hydrolysis to speed up translation.

Translocator

A protein complex in the ER membrane that enables the import of polypeptides into the ER lumen during translation.

Co-translational Translocation

The process where translation is coupled with translocation into the ER lumen, mediated by the signal sequence.

Post-Translational Translocation

The mechanism that allows polypeptides to be transported into the ER lumen after translation is complete, requiring chaperones and ATP.

Sec61 Complex

A translocator complex in the ER membrane that facilitates the translocation of polypeptides across the lipid bilayer.

Start-Transfer Signal

A hydrophobic signal peptide that initiates the insertion of a polypeptide into the membrane during co-translational translocation.

Stop-Transfer Signal

A transmembrane domain that halts further translocation of a polypeptide, allowing it to reside within the membrane.