Cellular Signaling and Protein Phosphorylation
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What is one of the main roles of protein phosphorylation in cellular signaling?

  • It stabilizes protein structures.
  • It transduces information along protein cascades. (correct)
  • It prevents protein degradation.
  • It enhances the binding affinity of all proteins.

    • Which residues are involved in the process of protein phosphorylation?

  • Glycine, proline, and asparagine
  • Cysteine, methionine, and phenylalanine
  • Alanine, valine, and leucine
  • Tyrosine, threonine, or serine (correct)

    • Which statement about structural domains is correct?

  • All structural domains perform the same functions.
  • There are typically no more than two structural domains in proteins.
  • Domains can have the same structure but differ in function. (correct)
  • Structural domains cannot be modular.

    • What is the significance of chemical modification in proteins?

    <p>It serves as a signal for regulating downstream signaling events.</p> Signup and view all the answers

    What does it mean for a structural domain to be described as modular?

    <p>It can form repeated regions within the same polypeptide or across different proteins.</p> Signup and view all the answers

    What is the primary function of receptor tyrosine kinases (RTKs)?

    <p>To catalyze phosphorylation of protein substrates</p> Signup and view all the answers

    Which domains are specifically involved in binding oligopeptide motifs?

    <p>SH2, SH3, and PTB domains</p> Signup and view all the answers

    What role does PTEN play in cellular signaling?

    <p>It functions as a dual-specificity protein phosphatase</p> Signup and view all the answers

    Which statement about Grb2 is true?

    <p>It interacts with the phospho tyrosine of RTKs through its SH2 domain.</p> Signup and view all the answers

    Which of the following motifs is involved in binding to phosphoinositides?

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

    What is the characteristic feature of SH2 domains?

    <p>They bind specifically to motifs containing a phosphotyrosine.</p> Signup and view all the answers

    Which domains provide sites for interaction with other proteins but do not have enzymatic activity?

    <p>Structural interaction domains</p> Signup and view all the answers

    Which proteins are examples of those containing SH2 domains?

    <p>Receptor tyrosine kinases and non-RTKs</p> Signup and view all the answers

    What is the main function of PDZ domains?

    <p>Anchor transmembrane proteins to the cytoskeleton</p> Signup and view all the answers

    Which of the following motifs is involved in calcium binding?

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

    What do the first letters of the acronym PDZ stand for?

    <p>Post synaptic density protein</p> Signup and view all the answers

    Which type of domains are considered to have intrinsic catalytic activity?

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

    What happens in the signaling pathway activated by light in Drosophila photoreceptors?

    <p>Coupling of receptor to Gq</p> Signup and view all the answers

    What does a loss of the InaD scaffold result in?

    <p>Retardation of visual resolution</p> Signup and view all the answers

    Which of the following is an example of a phosphoinositide-binding domain?

    <p>C2 domain</p> Signup and view all the answers

    What is the purpose of the coupling of PKC to PLCβ via the InaD scaffold?

    <p>To facilitate calcium release</p> Signup and view all the answers

    What is the primary role of a PDZ binding motif?

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

    Which of the following statements is true about scaffold proteins?

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

    Which of the following is NOT a characteristic of MAGUK proteins?

    <p>Contain an active guanylate kinase domain</p> Signup and view all the answers

    What type of proteins does the InaD protein function primarily with in fruit flies?

    <p>Phototransduction cascade proteins</p> Signup and view all the answers

    How does the PDZ domain interact within PDZ-based scaffold proteins?

    <p>Through peptide interactions recognizing specific sequences</p> Signup and view all the answers

    Which of the following correctly describes the domains found in MAGUK proteins?

    <p>PDZ domain, SH3 domain, and GUK domain</p> Signup and view all the answers

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

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

    What is a key characteristic of proline-rich sequences recognized by SH3 domains?

    <p>They generally consist of 8–10 residues of Pro.</p> Signup and view all the answers

    Which of the following statements best describes PDZ- and nonPDZ-based scaffold proteins?

    <p>PDZ-based scaffold proteins can interact with a diverse range of signaling partners.</p> Signup and view all the answers

    Which proteins are examples of those that contain SH3 domains?

    <p>Adaptor proteins such as Grb2 and Nck.</p> Signup and view all the answers

    Which domain is known for binding phosphotyrosine residues?

    <p>PTB domain.</p> Signup and view all the answers

    What is the physiological significance of PH domains?

    <p>They play a role in protein–protein interactions.</p> Signup and view all the answers

    Which of the following statements is true regarding Src family kinases?

    <p>They are involved in regulating cellular processes.</p> Signup and view all the answers

    What ability do PTB domains have that is not shared with SH2 domains?

    <p>To recognize sequences distinctly from phoshotyrosine motifs.</p> Signup and view all the answers

    PH domains primarily bind to which type of ligands?

    <p>Phosphoinositides.</p> Signup and view all the answers

    Which of the following best describes the structural characteristic of SH3 domains?

    <p>They possess a hydrophobic binding surface.</p> Signup and view all the answers

    What type of structural motif is the EF-hand motif primarily associated with?

    <p>Calcium binding</p> Signup and view all the answers

    Which domain is characterized by its ability to bind phosphoinositides?

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

    Which of the following domains is specifically recognized for binding oligopeptide motifs?

    <p>SH2 and SH3 domains</p> Signup and view all the answers

    What is the structural arrangement of the GRK2 PH domain?

    <p>Beta-sandwich structure</p> Signup and view all the answers

    What type of ion do C2 domains primarily bind?

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

    Which of the following correctly describes the coordination of the Ca2+ ion in calmodulin's EF-hand region?

    <p>Involves a helix-loop-helix structure</p> Signup and view all the answers

    The C2H2 zinc finger domain is named due to the presence of which amino acids coordinating zinc?

    <p>Two cysteines and two histidines</p> Signup and view all the answers

    What characterizes the structure of PH domains?

    <p>Antiparallel beta strands</p> Signup and view all the answers

    Study Notes

    Bioc 325: Lecture 2

    • Learning Objectives:
      • Introduce the structure, function, and different types of signaling structural domains.
      • Understand the roles of structural domains in signal propagation between signaling proteins.
      • Introduce scaffold proteins and their role in signal propagation.
    • Signaling Proteins:
      • Serve as building blocks.
      • Have special structural domains aiding cross-recognition, binding, and signal propagation.
    • Signal Initiation:
      • Begins with ligand interaction with its cognate receptor,
      • Inducing stoichiometric and conformational changes.
    • Signal Transduction Cascades:
      • Involve protein-protein interactions and protein phosphorylation.

    Protein-Protein Interactions

    • Essential for Signal Propagation:
      • Signal transfer across the intracellular space relies on proteins interacting with each other.
      • Interactions maintain signal specificity until the target is achieved (e.g., gene promoters).
      • These interactions are tightly controlled and not random, limited to specific authorized partners.
      • Protein modules (interaction motifs) are crucial for these processes.

    Protein Phosphorylation

    • Mechanism for Information Transduction:
      • A key mechanism in protein cascade information transfer.
      • Phosphorylation occurs when a protein kinase interacts with tyrosine, threonine, or serine residues.
      • Considered a signal to either activate or deactivate downstream signaling events.

    Part 1: Structural Domains

    • Definition:

      • Regions within proteins with similar architecture, specific spatial arrangements, and functional roles.
      • Modular structures, forming repeating modules or recurring structures throughout proteins.
      • Some domains have different structures yet identical functions, for instance, PTB and SH2 domains in binding pTyr.

    • Variations:

      • Other domains have similar structures but different functions (ex: PTB and PH domains).
      • Most signaling molecules contain multiple domains.

    • Functional Considerations:

      • A specific structural domain may confer a function but may not guarantee it due to mutations or exon shuffling within the gene encoding the domain.

    • Classification:

      • Catalytic Domains: Have enzymatic activity(ex: protein kinases, protein phosphatases).
      • Protein Interaction Domains: Do not have enzymatic activity, primarily provide interaction sites for other proteins (ex: SH2 and SH3 domains).

    Part 2: PDZ- and nonPDZ-based Scaffold Proteins

    • Definition: Proteins associating with two or more other proteins to enhance efficiency and specificity of a cellular pathway.
    • Types:
      • PDZ-based: Include InaD, PSD-95, NHERF, MAGUK.
      • Non-PDZ-based: Include AKAP, JAK-STAT, and β-arrestin.

    PDZ Domains

    • Function: Binding to C-terminal residues of some ion channels and receptors, as well as phosphoinositides.
      • Function in anchoring transmembrane proteins to the cytoskeleton.
      • Aid in holding together signaling complexes.

    MAGUK Proteins

    • Description: A specific type of PDZ-based scaffold protein characterized by specific domains ( PDZ, SH3, and GUK).
      • MAGUK proteins are characterized by having a PDZ domain, an SH3 domain, and a GUK (guanylate kinase) domain.
      • Serve as scaffolds for organizing signaling pathways.

    NonPDZ-based Proteins

    • Examples:

      • AKAP (A-kinase anchoring protein)
      • JAK-STAT (Janus kinases and STATs).
      • β-arrestin

    • Function:

      • AKAPs anchor protein kinases,
      • JAK proteins facilitate signaling cascades.
      • β-arrestins are involved in GPCR regulation.

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    Description

    Explore the key concepts of protein phosphorylation and its impact on cellular signaling in this quiz. Delve into the roles of structural domains and the significance of chemical modifications in proteins. Perfect for students seeking to enhance their understanding of molecular biology.

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