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ER Processing and Transport definitions

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  • Co-translational Import
    Entry of a polypeptide into the ER during its synthesis, guided by a signal sequence and involving the SRP and translocon.
  • Post-translational Import
    Translocation of a fully synthesized, unfolded polypeptide into the ER, requiring chaperone assistance for refolding.
  • ER Signal Sequence
    A short amino acid motif on nascent proteins that directs ribosomes to the ER for protein targeting.
  • Signal Recognition Particle
    A ribonucleoprotein that binds the ER signal sequence and pauses translation until docking at the ER membrane.
  • Translocon
    A protein-conducting channel in the ER membrane that facilitates polypeptide passage into the ER lumen.
  • Signal Peptidase
    An enzyme that cleaves the ER signal sequence from a newly translocated protein, finalizing its entry.
  • Single-pass Transmembrane Protein
    A membrane protein that spans the lipid bilayer only once, using one start and one stop transfer sequence.
  • Multi-pass Transmembrane Protein
    A membrane protein that traverses the lipid bilayer multiple times, dictated by alternating start and stop sequences.
  • Start Transfer Sequence
    A hydrophobic segment that initiates insertion of a polypeptide into the ER membrane via the translocon.
  • Stop Transfer Sequence
    A hydrophobic segment that halts further translocation, anchoring the protein within the membrane.
  • Glycosylation
    Attachment of sugar chains to proteins in the ER, crucial for proper folding and quality control.
  • Dolichol
    A lipid-linked oligosaccharide precursor that serves as the foundation for N-linked glycosylation in the ER.
  • GPI Anchor
    A glycolipid added to proteins in the ER, targeting them for attachment to the plasma membrane.
  • Protein Disulfide Isomerase
    An enzyme that catalyzes formation and rearrangement of disulfide bonds, stabilizing protein structure in the ER.
  • Unfolded Protein Response
    A quality control mechanism that detects misfolded proteins in the ER and targets them for degradation.
  • ERAD Proteins
    Factors that recognize and transport misfolded ER proteins to the cytosol for degradation.