protein trafficking
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Questions and Answers

What is the purpose of treating cells with [35S]methionine for 0.5h?

  • To label all newly synthesized proteins (correct)
  • To study cellular respiration
  • To remove all proteins from the cell
  • To induce mutations in proteins

    • How are proteins visualized after being fractionated from the ER, Golgi, and membrane?

  • By conducting PCR
  • Using autoradiography (correct)
  • By using electron microscopy
  • Through western blotting

    • In the context of protein sorting and secretion, what is the role of membrane-bound vesicles?

  • Acting as energy storage sites in the cell
  • Transporting protein cargo into, out-of, and within the cell (correct)
  • Serving as protective barriers around the nucleus
  • Anchoring proteins to the cell membrane

    • What is responsible for sending out proteins to the correct place inside or outside the cell?

    <p>Endoplasmic Reticulum</p> Signup and view all the answers

    Which organelle is involved in sorting proteins to the plasma membrane or to lysozymes?

    <p>Golgi Apparatus</p> Signup and view all the answers

    What is the purpose of the N-terminal signal sequence in proteins?

    <p>Guides the ribosome to the Endoplasmic Reticulum</p> Signup and view all the answers

    Which step involves opening of the translocon to allow insertion of the signal sequence and the growing peptide chain?

    <p>Protein synthesis and translocation across the ER membrane</p> Signup and view all the answers

    Where are carbohydrate chains added to proteins in glycosylation of proteins?

    <p>Carboxyl groups of serine/threonine</p> Signup and view all the answers

    Which type of glycosylation involves adding 1 - 4 carbohydrate residues?

    <p>O-linked glycosylation</p> Signup and view all the answers

    What is the function of protein disulfide isomerase (PDI) in the ER?

    <p>Assisting in Cys-Cys bond formation</p> Signup and view all the answers

    Which enzyme is responsible for adding the first sugar to Dolicol phosphate in N-linked glycan biosynthesis?

    <p>Pyrophosphatase</p> Signup and view all the answers

    What triggers the unfolded protein response in the ER?

    <p>Accumulation of unfolded proteins</p> Signup and view all the answers

    What is the role of Ire1 in the unfolded protein response?

    <p>RNA endonuclease</p> Signup and view all the answers

    Which structure is transferred to an Asp residue in the ER lumen during N-linked core glycan biosynthesis?

    <p>14-residue precursor</p> Signup and view all the answers

    What assists proteins in folding into their native conformation in the ER lumen?

    <p>Chaperones</p> Signup and view all the answers

    Which lipid is involved in the addition of sugars during N-linked core glycan biosynthesis?

    <p>Dolicol phosphate</p> Signup and view all the answers

    What happens when a protein receives a 'stop transfer' signal during insertion into the ER membrane?

    <p>The protein is left inserted in the ER membrane.</p> Signup and view all the answers

    In the secretory pathway, where do proteins destined for lysosomes go?

    <p>Trans-golgi network (TGN)</p> Signup and view all the answers

    How are proteins moved from the golgi apparatus back to the ER during the secretory pathway?

    <p>Transport by retrograde vesicles</p> Signup and view all the answers

    Where are proteins that are destined for regulated secretion sent by the trans-golgi network (TGN)?

    <p>Plasma membrane</p> Signup and view all the answers

    Which vesicles are responsible for transporting golgi resident proteins back to an earlier portion of the golgi?

    <p>Retrograde vesicles</p> Signup and view all the answers

    What is the main function of the golgi complex in the secretory pathway?

    <p>Sorting proteins to the plasma membrane or lysosomes</p> Signup and view all the answers

    Which structure is responsible for directing ribosomes with N-terminal signal sequences to the endoplasmic reticulum?

    <p>Signal Recognition Particle (SRP)</p> Signup and view all the answers

    In the co-translational translocation of proteins, what is required for SRP to target the ribosome to the ER membrane?

    <p>GTP</p> Signup and view all the answers

    Which step in protein secretion involves the insertion of the signal sequence and the growing peptide chain into the translocon?

    <p>Protein synthesis and translocation across the ER membrane</p> Signup and view all the answers

    What is the specific function of the N-terminal signal sequence in proteins that need to be sorted within the cell?

    <p>Guide ribosomes to endoplasmic reticulum</p> Signup and view all the answers

    What is the unifying principle of both the secretory and endocytic pathways?

    <p>Use of membrane-bound vesicles</p> Signup and view all the answers

    In vesicle docking, what proteins are responsible for the fusion of a vesicle with its target membrane?

    <p>SNAP Receptor proteins</p> Signup and view all the answers

    Which type of vesicle is responsible for transporting proteins from the rough ER to the Golgi?

    <p>COP II</p> Signup and view all the answers

    What initiates vesicle budding in the process of vesicle formation?

    <p>Recruitment of small GTP-binding proteins</p> Signup and view all the answers

    Which proteins ensure that a vesicle fuses with the correct target membrane during vesicle docking?

    <p>v-SNARE proteins</p> Signup and view all the answers

    Which technique is used to label all newly synthesized proteins in cells?

    <p>Autoradiography</p> Signup and view all the answers

    In the context of studying genetic secretory mutants, what can one investigate using genetic engineering and mutagenesis?

    <p>Effects of clinically relevant mutations or therapeutic molecules on the secretory pathway</p> Signup and view all the answers

    What is the main purpose of treating cells with non-isotopic methionine after labeling with [35S]methionine?

    <p>Label newly synthesized proteins for further analysis</p> Signup and view all the answers

    Which organelles are proteins fractionated from after being labeled with [35S]methionine?

    <p>Endoplasmic reticulum, Golgi, and membrane</p> Signup and view all the answers

    What is the significance of using membrane-bound vesicles in protein transport within the cell?

    <p>To transport protein cargo into, out-of, and within the cell</p> Signup and view all the answers

    What is the main function of the rough ER in protein sorting and secretion?

    <p>Completion of translation for secretory proteins</p> Signup and view all the answers

    In the context of the secretory pathway, what is the significance of transport vesicles?

    <p>Facilitate movement of proteins from rough ER to Golgi complex</p> Signup and view all the answers

    How are non-secreted cytosolic proteins distinguished from secretory proteins in terms of their generation?

    <p>Non-secreted proteins are generated on cytosolic ribosomes without any specific signaling sequence.</p> Signup and view all the answers

    What is the fate of secretory proteins after passing through the Golgi complex?

    <p>Secretory proteins are released outside the cell</p> Signup and view all the answers

    In protein sorting, what would be the consequence if a protein lacks an ER signal sequence?

    <p>The protein will not be secreted and will complete translation in the cytosol.</p> Signup and view all the answers

    What is the role of Sar1 in vesicle formation during the secretory pathway?

    <p>Anchors into the membrane via a hydrophobic tail</p> Signup and view all the answers

    Which protein is responsible for the stable docking and membrane fusion of vesicles in the secretory pathway?

    <p>VAMP</p> Signup and view all the answers

    How do ER luminal proteins get retrieved from the golgi back to the ER in the secretory pathway?

    <p>Incorporated into COP II vesicles and transported back</p> Signup and view all the answers

    Which protein is involved in dissociating the SNARE complex during membrane fusion in the secretory pathway?

    <p>NSF</p> Signup and view all the answers

    What is the function of the KDEL receptor in protein trafficking?

    <p>Retrieving ER resident proteins from the golgi</p> Signup and view all the answers

    What is the role of Ero1 in the ER lumen?

    <p>Forming and rearranging disulfide bonds</p> Signup and view all the answers

    Which protein is responsible for catalyzing Cys-Cys bond formation in secretory or membrane-bound proteins?

    <p>PDI</p> Signup and view all the answers

    In the context of glycosylation of proteins, which amino acid residue is involved in O-linked carbohydrate chain addition?

    <p>Threonine</p> Signup and view all the answers

    What is the primary function of Ire1 in protein quality control in the ER?

    <p>Activating translation of Hac1 protein</p> Signup and view all the answers

    What is the significance of Dolicol phosphate (DP) in N-linked core glycan biosynthesis?

    <p>It adds the first sugar via pyrophosphate linkage</p> Signup and view all the answers

    Which process is visualized by fluorescence microscopy using GFP-tagged proteins?

    <p>Protein transport through the secretory pathway</p> Signup and view all the answers

    What is the primary function of chaperones in the ER lumen?

    <p>Helping fold proteins into their native conformation</p> Signup and view all the answers

    In N-linked glycan biosynthesis, what is the role of the 7 residue intermediate that is 'flipped' across the ER membrane?

    <p>'Flips' to transfer sugars to Asp residue in the ER lumen</p> Signup and view all the answers

    Study Notes

    Protein Synthesis and Sorting

    • Treating cells with [35S]methionine for 0.5h labels all newly synthesized proteins.
    • The purpose of this treatment is to visualize proteins after fractionation from the ER, Golgi, and membrane.

    Protein Trafficking and Secretion

    • Membrane-bound vesicles play a crucial role in protein sorting and secretion.
    • They are responsible for sending proteins to the correct place inside or outside the cell.
    • The Golgi apparatus is involved in sorting proteins to the plasma membrane or to lysosomes.
    • The N-terminal signal sequence is responsible for directing proteins to the correct location.

    Protein Modification and Folding

    • The N-terminal signal sequence is inserted into the translocon during protein synthesis.
    • Carbohydrate chains are added to proteins in the Golgi apparatus during glycosylation.
    • O-linked glycosylation involves adding 1-4 carbohydrate residues.
    • Protein disulfide isomerase (PDI) helps proteins fold into their native conformation in the ER lumen.

    ER Quality Control

    • The unfolded protein response (UPR) is triggered by the accumulation of unfolded proteins in the ER.
    • Ire1 plays a key role in the UPR, helping to maintain ER homeostasis.
    • Protein disulfide isomerase (PDI) also helps to correct protein folding in the ER.

    Vesicle Formation and Transport

    • Vesicle budding is initiated by the formation of a bud on the ER membrane.
    • Sar1 is involved in vesicle formation during the secretory pathway.
    • SNARE proteins are responsible for the fusion of vesicles with their target membrane.
    • Rab proteins ensure that vesicles fuse with the correct target membrane.

    Golgi Apparatus and Protein Secretion

    • The Golgi apparatus is responsible for sorting and modifying proteins for secretion.
    • Proteins destined for regulated secretion are sent to the trans-Golgi network (TGN).
    • Vesicles that transport proteins from the rough ER to the Golgi are called COPII vesicles.
    • The main function of the Golgi apparatus is to modify and sort proteins for secretion.

    Protein Quality Control and Retrieval

    • The KDEL receptor is involved in protein retrieval from the Golgi back to the ER.
    • Ero1 is responsible for catalyzing Cys-Cys bond formation in secretory or membrane-bound proteins.
    • Chaperones in the ER lumen help proteins fold into their native conformation.
    • The 7-residue intermediate is involved in N-linked core glycan biosynthesis.

    Visualization and Analysis

    • Fluorescence microscopy using GFP-tagged proteins can visualize protein trafficking and secretion.
    • Genetic engineering and mutagenesis can be used to investigate protein secretion and sorting in genetic secretory mutants.
    • Treating cells with non-isotopic methionine after labeling with [35S]methionine can be used to analyze protein synthesis and secretion.

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    Protein Trafficking 2024 PDF

    Description

    Test your knowledge on protein post-translational modifications such as glycosylation and covalent stabilization through Cys-Cys bond formation. Learn about the assembly of multi-subunit conformations and cleavage into active forms. Understand the different types of glycosylation involving serine, threonine, and asparagine residues.

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