Unit 1: Ligand Binding Flashcards
What’s a ligand?
A ligand is a substance that can bind to a
protein
What happens as a result of ligand binding
As a ligand binds to a protein-binding site the
conformation of the protein changes
This change in conformation causes a
functional change in the protein
Whats an allosteric enzyme?
Allosteric enzymes are enzymes that are regulated by changing their conformation and contain a second type of
site, called an allosteric site.
Whats a modulator?
Modulators regulate the activity of the
enzyme when they bind to the allosteric site
What happens after a modulator binds to an allosteric enzyme?
Following binding of a modulator, the
conformation of the enzyme changes and this
alters the affinity of the active site for the
substrate
Whats the difference between positive and negative modulators?
Positive modulators increase the enzyme’s
affinity for the substrate, whereas negative
modulators reduce the enzyme’s affinity.
How does haemoglobin show cooperativity with oxygen?
When the first oxygen ligand binds to one of the subunits it alters the conformation of the haemoglobin. Thisincreases the affinity of the other subunits for oxygen making it easier for the other 3 oxygen molecules to bind to the other 3 subunits.
How does temperature and pH affect the binding of oxygen to haemoglobin?
A decrease in pH or an increase in
temperature lowers the affinity of haemoglobin
for oxygen, so the binding of oxygen is
reduced. Reduced pH and increased
temperature in actively respiring tissue will
reduce the binding of oxygen to haemoglobin
promoting increased oxygen delivery to tissue
What can the addition or a removal of a phosphate cause?
A reversible conformational change in the protein
What is the addition or removal of a phosphate a common form of?
Post-translational modification
What do kinases do?
Protein kinases catalyse the transfer of a
phosphate group to other proteins
What do phosphatases do?
Protein phosphatases catalyse the reverse
reaction
