Cell Signaling and Protein Domains Quiz
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What is the primary role of protein phosphorylation in cellular processes?

  • It prevents protein-protein interactions.
  • It transduces information along protein cascades. (correct)
  • It initiates protein translation.
  • It modifies the structure of proteins permanently.

    • Which of the following statements about structural domains is true?

  • Each structural domain has a unique protein folding structure.
  • A single protein can contain multiple distinct structural domains. (correct)
  • Domains are always identical in structure and function.
  • Structural domains can only be found in signaling molecules.

    • What process contributes to the variability of structural domains in proteins?

  • Transcription regulation
  • Mutations and shuffling of exons (correct)
  • Protein degradation
  • Translation errors

    • Which of the following is an example of a catalytic domain?

    <p>Protein kinase domain</p> Signup and view all the answers

    What distinguishes PTB and SH2 domains from each other?

    <p>Both domains have different structures but bind the same type of target.</p> Signup and view all the answers

    How do cellular proteins interpret chemical modifications such as phosphorylation?

    <p>As signals to either activate or deactivate signaling pathways.</p> Signup and view all the answers

    What happens to the tetrameric structure of PKA when four cAMP molecules bind to its regulatory subunits?

    <p>It dissociates into active catalytic monomers.</p> Signup and view all the answers

    Which of the following statements accurately reflects the nature of structural domains?

    <p>Most proteins contain at least two structural domains.</p> Signup and view all the answers

    Which domain is associated with enzymatic activity specifically related to removing phosphate groups?

    <p>Protein phosphatase domain</p> Signup and view all the answers

    What is the role of the protein interaction domains?

    <p>Enabling communication between proteins</p> Signup and view all the answers

    What initiates the intracellular signaling process?

    <p>Binding of a ligand to its cognate receptor</p> Signup and view all the answers

    Which mechanism is NOT involved in signal transduction cascades within a cell?

    <p>Signal amplification</p> Signup and view all the answers

    How do structural domains of signaling proteins contribute to signal propagation?

    <p>They assist in the specific binding and interaction with other proteins.</p> Signup and view all the answers

    What is the primary role of scaffold proteins in signaling pathways?

    <p>To enhance the specificity and efficiency of signal transmission.</p> Signup and view all the answers

    What is the significance of non-covalent interactions between signaling proteins?

    <p>They maintain signal specificity until the final target is reached.</p> Signup and view all the answers

    Which of the following best describes protein-protein interactions in signaling cascades?

    <p>They are tightly controlled and restricted to authorized partners.</p> Signup and view all the answers

    What happens to the ligand-receptor complex upon binding?

    <p>It induces structural changes leading to signal initiation.</p> Signup and view all the answers

    Why is signal specificity important in intracellular signaling?

    <p>It ensures that signals only affect appropriate target components.</p> Signup and view all the answers

    What is the main characteristic of proline-rich sequences that SH3 domains interact with?

    <p>Include at least two prolines in a PxxP motif</p> Signup and view all the answers

    Which of the following proteins is an example of a protein containing SH3 domains?

    <p>Grb2</p> Signup and view all the answers

    Which type of domain binds to phosphotyrosine residues?

    <p>PTB domains</p> Signup and view all the answers

    What is a key function of PH domains in cellular processes?

    <p>Interaction with acidic phospholipid head groups</p> Signup and view all the answers

    What is the general role of Src family kinases in cellular processes?

    <p>Regulating fundamental cellular processes</p> Signup and view all the answers

    Which protein is cited as an example of a PH-domain containing protein?

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

    In which structural conformation do Src family kinases become active?

    <p>Open active conformation</p> Signup and view all the answers

    Which domain is specifically associated with calcium binding?

    <p>EF-hand motifs</p> Signup and view all the answers

    What is the primary function of a PDZ binding motif?

    <p>To recognize and bind other signaling molecules</p> Signup and view all the answers

    Which of the following proteins is considered a PDZ-based scaffold protein?

    <p>PSD-95</p> Signup and view all the answers

    What characterizes MAGUK proteins?

    <p>Presence of PDZ, SH3, and GUK domains</p> Signup and view all the answers

    Which of the following is a function of scaffold proteins?

    <p>To enhance efficiency and specificity of cellular pathways</p> Signup and view all the answers

    Which scaffold protein is involved in the Drosophila melanogaster phototransduction cascade?

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

    Which domain is NOT found in MAGUK proteins?

    <p>SH2 domain</p> Signup and view all the answers

    What does the abbreviation 'MAGUK' stand for?

    <p>Membrane-Associated Guanylate Kinases</p> Signup and view all the answers

    Which protein is known as the Na H Exchanger regulatory factor?

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

    What is the primary role of AKAP in cellular signaling?

    <p>Anchors protein kinase A for receptor phosphorylation</p> Signup and view all the answers

    Which of the following proteins directly interacts with phosphorylated receptors?

    <p>β-arrestin</p> Signup and view all the answers

    Which kinases are non-covalently associated with cytokine receptors to initiate signaling?

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

    How do STATs become activated after binding to the phosphorylated receptor?

    <p>Through dimerization and translocation to the nucleus</p> Signup and view all the answers

    What distinguishes cytokine receptors from receptor tyrosine kinases (RTKs)?

    <p>Cytokine receptors lack intrinsic catalytic domains</p> Signup and view all the answers

    What role does the COOH-terminal end of G-protein coupled receptors (GPCRs) serve?

    <p>Binds to non-PDZ based scaffold proteins</p> Signup and view all the answers

    Which domain of STATs is crucial for their binding to phosphorylated receptors?

    <p>SH2 domain</p> Signup and view all the answers

    Which of the following is NOT considered a signaling scaffold protein?

    <p>JAK1</p> Signup and view all the answers

    Study Notes

    Bioc 325: Lecture 2

    • Learning Objectives: Introduce signaling structural domains, their roles in signal propagation, and the importance of scaffold proteins.

    • Introduction: Intracellular signaling translates messages for cellular responses. The initial step involves ligand-receptor interaction causing conformational changes. Common mechanisms include protein-protein interactions and phosphorylation.

    • Protein-Protein Interactions: Signal propagation through the intracellular space requires protein interaction. It maintains signal specificity and occurs in a tightly controlled mode, not randomly. Protein interactions are restricted to authorized partners. Protein modules (interaction motifs) are key.

    • Protein Phosphorylation: A popular mechanism for transmitting information along cascades. It occurs when a protein kinase interacts with tyrosine, threonine, or serine residues on a protein which serves as a signal for activating or deactivating downstream events.

    • Part 1: Structural Domains:

      • Domains are regions of similar architecture within proteins, serving as functional components.
      • Domains are modular, repeating within a single polypeptide or recurring in various protein structures.
      • Some domains have different structures but the same function (e.g., PTB and SH2 bind p-Tyr).
      • Some domains have the same structure but different functions (e.g., PTB and PH).
      • Most proteins contain at least two domains and signaling molecules often have more.

    • Structural Domains and Their Roles:

      • Domains play key roles as functional components.
      • Individual domains may not guarantee a specific function but may contribute to it.
      • Exon mutations and shuffling affect a domain's function.

    • A: Catalytic Domains: Possess enzymatic activity. Examples include protein kinase domains (like PKA, PKC, RTKs) and phosphatase domains (like PTEN).

    • B: Protein Interaction Domains: Lack enzymatic activity. These provide interaction sites for other proteins. Examples include SH2 and SH3 domains.

    • Classification of Structural Domains: Domains are classified by their function in cellular signaling:

      • Domains that bind to oligopeptide motifs (SH2, SH3, PTB)
      • Phosphoinositide-binding domains (PH)
      • Ca2+-binding domains (EF-hand and C2)
      • Zinc finger domains (C2H2)
      • Protein kinase domains
      • PDZ domains

    SH2 Domains

    • Nomenclature: SH2 = Src homology region 2.
    • Function: Protein interaction domains that bind to short motifs with phosphotyrosine.
    • Examples: Receptor tyrosine kinases (RTKs), non-RTKs, phospholipase Cy (PLCγ), regulatory subunits of phosphoinositide 3-kinase (PI3K), and some protein tyrosine phosphatases (PTPs).

    SH3 Domains

    • Nomenclature: SH3 = Src homology region 3.
    • Function: Protein interaction domains that bind to proline-rich sequences.
    • Proline-rich Sequences: Typically consist of 8-10 proline residues, including at least two prolines in a PxxP motif.
    • Hydrophobic Binding: SH3 domains have a hydrophobic binding surface.
    • Examples: Adaptor proteins such as Grb2 and Nck.

    PTB Domains

    • Nomenclature: PTB = PhosphoTyrosine Binding.
    • Function: Bind phosphotyrosine residues (N-P-X-pY), but recognize sequences that are quite distinct from SH2 domains.
    • Phospholipid Binding: Also can bind acidic phospholipid head groups like those in phosphoinositides.
    • Importance: Can translocate to membrane surfaces to encounter ligands.
    • Example: PTB domain of insulin receptor substrate-1 (IRS-1).

    PH Domains

    • Nomenclature: PH = Pleckstrin Homology.
    • Physiological Ligands: Phosphoinositides and βy-subunits of G proteins.
    • Role: Involved in protein-protein interactions.
    • Role: Example: Interaction of GRK2 (G-protein receptor kinase 2) with activated β-adrenergic receptors.
      • Examples: pleckstrin, GRK2, PLC, Akt

    Ca2+ binding motifs

    • EF-hand motifs: Helix-loop-helix motifs that recognize and bind to calcium. Typically occur as adjacent pairs for enhanced function.
    • C2 domains: Second conserved regulatory domain of PKCB, recognizing and binding to calcium.

    Zinc Finger Domains

    • C2H2 Domains: The largest zinc finger family, where zinc is coordinated by two cysteine and two histidine residues forming a stable complex.

    Protein Kinase Domains

    • Function: Catalytic domains with intrinsic activity. Examples are the catalytic subunits of PKA, PKC, RTKs

    PDZ Domains

    • Function: Bind to C-terminal residues of ion channels and receptors. Some can also bind to phosphoinositides. They help to anchor transmembrane proteins to the cytoskeleton and hold signaling complexes together.

    Part 2: PDZ and Non-PDZ-based Scaffold Proteins

    • Definition: Proteins that associate with two or more other proteins to enhance the efficiency and/or specificity of a cellular pathway.

    PDZ-based Scaffold Proteins

    • Specific examples include InaD, PSD-95, NHERF, and MAGUK proteins.

    Non-PDZ-based Scaffold Proteins

    • Specific examples include AKAP, JAK-STAT, and β-arrestin.

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    Bioc 325 Lecture 2 2023 PDF

    Description

    Test your knowledge on the roles of protein phosphorylation and structural domains in cellular processes. Explore how modifications like phosphorylation influence signaling pathways and the interactions among proteins. Challenge yourself with questions about catalytic domains and the nature of signal transduction.

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