Moving Proteins into Membranes and Organelles, Part 1

These flashcards cover key vocabulary and concepts related to the structure, function, and processes of the Endoplasmic Reticulum and protein targeting.

Endoplasmic Reticulum (ER)

A network of membranes involved in protein synthesis, modifications, and quality control.

Signal Sequence

An amino acid sequence that directs proteins to their proper location in the cell.

SRP (Signal Recognition Particle)

A ribonucleoprotein that recognizes signal sequences and facilitates protein targeting to the ER.

Translocon

A protein complex that forms a channel in the ER membrane for the translocation of nascent proteins.

Cotranslational Insertion

The process where polypeptides are inserted into the ER membrane while still being synthesized.

Lumen

The internal environment of the ER where proteins are folded and modified.

Rough ER

The region of the ER studded with ribosomes, involved in protein synthesis for secretion or membrane insertion.

Signal Peptidase

An enzyme that cleaves signal sequences from proteins after translocation into the ER.

Biosynthesis of Oligosaccharides

The process of adding carbohydrate chains to proteins within the rough ER.

Calnexin

A chaperone protein in the ER that assists in the proper folding of glycoproteins.

Quality Control

The process by which cells ensure only correctly folded proteins are allowed to exit the ER.

Dislocation

The process of removing misfolded proteins from the ER back to the cytosol for degradation.

BiP (Binding Immunoglobulin Protein)

A chaperone protein that assists in the folding and assembly of nascent proteins in the ER.

GPI (Glycosylphosphatidylinositol) Anchored Proteins

Proteins that are covalently attached to a lipid anchor in the membrane via a GPI moiety.

Transmembrane Domain

A segment of a protein that spans across the lipid bilayer of a membrane.

Hydropathy Profile

A graphical representation indicating the hydrophobic or hydrophilic nature of segments of a protein.

Post-Translational Translocation

The process where proteins are imported into the ER after they have been fully synthesized.

Topogenic Sequences

Specific sequences in proteins that dictate their insertion and orientation within membranes.

Unfolded Protein Response (UPR)

A cellular stress response related to the endoplasmic reticulum that manages misfolded proteins.

Sec61 Complex

The translocon in the ER responsible for inserting nascent polypeptides into the membrane.

Integral Membrane Proteins

Proteins that are permanently attached to the membrane and can span the lipid bilayer.

Chaperones

Proteins that assist in the folding and assembly of other protein molecules.

Oligosaccharide Addition

The process of attaching carbohydrate chains to proteins as a modification in the ER.

Hydrophobic Core

The hydrophobic region of a signal sequence that interacts with the translocon during insertion.

Enzymatic Modifications

Alterations made to proteins by enzymes within the ER to ensure proper function.

Sarcoplasmic Reticulum

A specialized form of smooth ER found in muscle cells, involved in calcium storage.

Mitochondrial Proteins

Proteins that are targeted and translocated into mitochondria for their function.

Nuclear Envelope

The double membrane surrounding the nucleus through which nuclear proteins are transported.

Protein Folding

The process by which a protein achieves its functional three-dimensional structure.

Translocation Channel

A pathway through which polypeptides move during their translocation into the ER.

Sec63 Complex

A protein complex involved in the translocation of proteins into the ER.

Calreticulin

An ER chaperone that binds to newly synthesized glycoproteins to assist in folding.

Signal-anchor Sequence

An internal sequence that serves both as a signal for targeting to the membrane and an anchor.

BiP and ATP Hydrolysis

The mechanism by which BiP provides energy for the translocation of proteins across the ER membrane.