Lecture 2.1: Intro to Soluble Transport Proteins Flashcards
Many of protein functions involve binding
Binding occurs between?
- Enzymes & their substrates
- receptors & signal molecules
- transporters & small molecules (for transport)
A ligand is a
small molecule that forms a complex with a protein to serve a biological function
The binding of ligands to proteins occurs by [—] interactions
weak non-covalent interactions
ligand binding is a [—] association
Reversible
Ka
association constant/ equilibrium constant for the association (or binding of the protein and ligand)
Keq = Ka
[products]/[reactants] = [protein-ligand complex]/[protein][ligand]
Large Ka = [—]
high binding affinity
Small Ka = [—]
low binding affinity
Kd
dissociation constant/ equilibrium constant for the dissociation of ligand from protein-ligand complex
Keq = Kd
[reactants]/[products] = [protein][ligand]/[protein-ligand complex]
Large Kd = [–]
low binding affinity
small Kd = [–]
high binding affinity
fractional saturation
the fraction of protein binding sites that are occupied
fractional saturation equation
theta =(occupied binding site)/(total binding sites)=[PL]/([PL]+[P])=[L]/([L]+Kd )
Order of Protein Dissociation Constants from Low to High
Biotin-advin
Enzyme-substrate
Typical receptor-ligand interactions
Sequence-specific protein-DNA
Antibody-antigen
[High Affinity]
1. Biotin-avidin
2. Antibody-antigen
3. Sequence-specific protein-DNA
4. Typical receptor-ligand interactions
5. Enzyme-substrate
[Low Affinity]
