2) c) ii) Ligand Binding
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define a ligand
a ligand is a substance which can bind to a protein
_ groups not involved in _______ ________ can allow _____ to ______
R groups not involved in protein folding can allow binding to ligands
__________ _______ will have ___________ shape and chemistry to the ligand
Binding sites will have complementary shapes and chemistry to the ligand
When a ligand binds to a protein-binding site what happens to the conformation of the protein?
When a ligand binds to a protein-binding site the conformation of a protein changes. This binding causes a functional change in the protein
allosteric sites exist between _________ _______ ______.
Allosteric sites exist between spatially distinct sites.
Describe the process of the substrate molecule binding to an allosteric enzyme ACTIVE SITE and what happens as a result of this
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.
Many allosteric proteins consist of _______ _________ (they have a _________ __________)
Many allosteric proteins consist of multiple subunits (have quaternary structure)
Allosteric proteins with _________ subunits show ______________ in binding, in which ________ in ________ at _____ __________ alters the _________ of the remaining subunits.
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
Allosteric enzymes contain a second type of site, called an __________ _______
Allosteric enzymes contain a second type of site, called an allosteric site
What regulates the activity of the enzyme when it binds to the allosteric site?
Modulators regulate the activity of the enzyme when they bind to the allosteric site.
Allosteric interactions occur between _________ _______ ________.
Allosteric interactions occur between spatially distinct sites
Positive modulator _________ the _________ _______ for the ________ whilst negative modulators _________ the _________ _________.
Positive Modulators increase the enzyme’s affinity for the substrate whilst negative modulators reduce the enzymes affinity. (Upon binding a modulator, the conformation of an allosteric enzyme will change and this alters the affinity of the active site for the substrate.)
Name an example which shows co-operativity
The binding and release of oxygen in haemoglobin shows co-operativity.
How does the binding of oxygen influence the other subunits on haemoglobin?
Changes in binding of oxygen at one subunit alter the affinity of the remaining subunits for oxygen. When an oxygen molecule binds to one of the four subunits of haemoglobin, it increases the affinity of oxygen for the other subunits. When an oxygen molecule is released from one subunit it decreases the oxygen affinity of the other subunits - all the oxygens are released.
What are the two factors which can affect the binding of oxygen to haemoglobin
temperature increase ph decrease 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.