Protein Function: The immune system and motors Flashcards
What is a key feature of protein-ligand interactions?
They are often based on the presence of a cleft lined with amino acid R-groups.
How does protein conformation affect ligand binding?
The binding of ligands (e.g., O2 or CO) to the haem affects the protein’s conformation and vice versa
What is essential for binding sites in proteins?
They must effectively discriminate between ligands, even with small structural differences.
What is the role of the haem group in globins?
It binds oxygen and carbon monoxide, influencing the protein’s conformation
What is the significance of reversible ligand binding?
It is crucial for sensitive and specific biochemical systems.
What distinguishes “self” from “non-self” in the immune system?
All vertebrates possess an immune response that can make this distinction
What does the immune system eliminate?
Viruses, bacteria, and other pathogens, as well as foreign molecules.
What components are involved in the immune response?
Specialist proteins (e.g., immunoglobulins), small molecules (e.g., cytokines), and various cell types
What is the Major Histocompatibility Complex (MHC)?
A set of proteins on the surface of vertebrate cells that presents antigens to T-cellsv
How many class I MHC proteins can an individual produce?
Up to six class I MHC proteins.
What is the primary function of class I MHC proteins?
To signal to T-cells when cells are infected by viruses.
How many class II MHC proteins can an individual produce?
Up to twelve class II MHC proteins
What is an antigen?
A molecule recognized by the immune system
What is the role of the T cell receptor (TCR)?
It recognizes the MHC-antigen complex, crucial for the immune response
What is the humoral immune response?
The antibody-mediated immune response where antibodies bind to antigens
What is the structure of IgG antibodies?
Composed of four polypeptide chains: two light chains and two heavy chains
What is the total molecular weight of an IgG antibody?
Approximately 150 kDa.
What are the components of the light and heavy chains in antibodies?
Light chains: 1 constant domain and 1 variable domain; Heavy chains: 3 constant domains and 1 variable domain
What happens when an antibody is cut with papain?
It generates Fc and Fab fragments
What is the function of the Fab fragment?
It is responsible for antigen binding.
What stabilises immunoglobulin domains?
A disulfide bond
What is the typical structure of immunoglobulin domains?
A 7-9 stranded β-barrel with two antiparallel β-sheets
What is the significance of the hinge region in antibodies?
It allows antibodies to bind tightly and specifically to antigens.
What is the binding energy of antibodies to antigens?
Approximately -65 kJ/mol.
What is the equation for the dissociation constant (Kd) of antibody-antigen complexes?
Kd =
[Ab−Ag]/
[Ab][Ag]
What is the role of myosin in muscle contraction?
Myosin interacts with actin to facilitate muscle contraction.
What triggers muscle contraction?
The release of Ca²⁺ ions in response to nerve impulses.
What is the cross-bridge cycle?
The series of steps involving ATP binding and hydrolysis that leads to muscle contraction
What are the components of thick filaments in muscle?
Myosin II, consisting of two heavy chains and four light chains.
What is the function of ATP in muscle contraction?
It provides the energy needed for myosin to change conformation and interact with actin.
What are the components of thin filaments?
Monomeric actin (G-actin) that forms filamentous actin (F-actin).
How does ATP hydrolysis relate to actin assembly?
ATP is hydrolyzed to ADP during the assembly of actin, not during contraction.
What role does tropomyosin play in muscle contraction?
It covers myosin binding sites on actin, regulating contraction
What is the role of troponin in muscle contraction?
It binds Ca²⁺ ions, causing a conformational change that allows contraction.
What is the significance of the sarcomere structure?
It is the basic unit of muscle contraction, where thick and thin filaments slide past each other
What is Western Blotting?
A technique used to detect specific proteins in a sample using antibodies
What is immunohistochemistry?
A method for detecting specific antigens in tissues using antibodies.
What is the role of antibodies in experiments?
They are used to identify and quantify specific proteins or antigens.
What is the importance of antibody specificity?
It ensures that antibodies bind only to their specific epitopes.
What is an epitope?
The part of an antigen that is recognized by an antibody.
How do proteins achieve spatial and temporal organisation?
Through interactions with ligands and other proteins
What is the primary energy source for motor proteins?
ATP is the fuel for cyclical conformational changes in motor proteins
What is the effect of Ca²⁺ ions on muscle contraction?
They trigger conformational changes that allow actin and myosin interactions
What is the role of cytokines in the immune response?
They are small signaling molecules that mediate and regulate immunity.
What is the significance of immunoglobulins in the immune system?
They are key components of the antibody-mediated immune response.
What is the relationship between myosin heads and muscle contraction?
Only 1-3% of myosin heads are bound at any moment, preventing slippage
What is the Greek Key motif in immunoglobulin domains?
A structural arrangement that stabilizes the domain.
How do antibodies undergo conformational changes?
Binding to antigens often induces structural changes for better fit.
What is the role of disulfide bonds in antibodies?
They stabilize the overall structure of the antibody.
How does the immune response adapt to new pathogens?v
Through the generation of diverse antibodies that can bind to various epitopes.
