Protein Function and Ligand Binding in Globular Proteins

Ligand

Molecule that binds to a protein.

Binding Site

Region in protein where ligand attaches.

Myoglobin

Globular protein that stores oxygen.

Hemoglobin

Protein that transports oxygen in blood.

Cooperativity

Binding of ligand affects other binding sites.

Induced Fit

Conformational change upon ligand binding.

Equilibrium Constant (Ka)

Describes binding affinity, units M−1.

Dissociation Constant (Kd)

Indicates how easily ligand dissociates, units M.

Strong Binding

what does Kd < 10 indicate?

Weak Binding

What does Kd > 10 indicate?

Soret Band

Absorption peak of heme at specific wavelength.

Bohr Effect

pH change affects hemoglobin's oxygen affinity.

2,3-Bisphosphoglycerate

Regulates hemoglobin function, stabilizes T state.

Muscle Contraction

Involves actin and myosin interactions.

Actomyosin Cycle

Series of conformational changes during muscle contraction.

Troponin

Regulates myosin-binding sites on actin.

Tropomyosin

Blocks myosin-binding sites on actin.

Chemical Equilibrium

Reversible process of ligand binding.

Affinity

Strength of binding between ligand and protein.

Partial Pressure

Used to express gas ligand binding.

Conformational Change

Structural alteration in protein upon binding.

Tetramer

Protein composed of four subunits.

R State

Relaxed state of hemoglobin with high affinity.

T State

Tense state of hemoglobin with low affinity.

pO2

Partial pressure of oxygen in tissues.

Affinity Variability

Hemoglobin's affinity changes with oxygen concentration.

Oxygen Binding

Interaction between hemoglobin and oxygen.

Carbon Monoxide Binding

CO binds heme stronger than O2.

Sickle-Cell Anemia

Mutation in hemoglobin causing red blood cell distortion.