Ligand Binding Changes The Conformation of a Protein

Question 1

Ligand

Answer 1

A ligand is a substance that can bind to a protein.

Question 2

Ligand Binding

Answer 2

R groups not involved in protein folding can allow ligands to bind.

Binding sites will have a complementary shape and chemistry to the ligand.

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

Question 3

Allosteric interactions

Answer 3

Allosteric interactions occur between spatially
distinct sites

The binding of a substrate molecule to one
active site of an allosteric enzyme increases
the affinity of the other active sites for binding
of subsequent substrate molecules. This is of
biological importance because the activity of
allosteric enzymes can vary greatly with
small changes in substrate concentration.

Question 4

Many allosteric proteins consist of multiple
subunits
(have quaternary structure)

Answer 4

Allosteric proteins with multiple subunits show co-operativity in binding, in which changes in binding at one subunit alter the affinity of the remaining subunits

Question 5

Modulators

Answer 5

Modulators regulate the activity of the enzyme when they bind to the allosteric site

Following binding of a modulator, the conformation of the enzyme changes and this alters the affinity of the active site for the substrate.

Positive modulators increase the enzyme’s affinity for the substrate, whereas negative modulators reduce the enzyme’s affinity.

(Allosteric enzymes contain a second type of
site, called an allosteric site)

Question 6

The binding and release of oxygen in haemoglobin shows co-operativity

Answer 6

Changes in binding of oxygen at one subunit alter the affinity of the remaining subunits for oxygen.

The influence and physiological importance of temperature and pH on the binding of oxygen -

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