KA2: Proteins: Protein structure, ligand binding and conformational change: Ligand binding changes the conformation of a protein Flashcards
Define the term ligand
A substance that can bind to a protein
what do R groups not involved in protein folding do?
allow binding to ligands
binding sites will have…
complementary shape and chemistry to the ligand
what happens when a ligand binds to the protein-binding site?
and what does this do?
the conformation of the protein changes
this change in conformation causes a functional change in the protein
describe the allosteric interactions occuring between spatially distinct sites and why these interactions are of biological importance
*binding of substrate molecule to one active site of an allosteric enzyme increases the affinity of the other active sites for binding of a subsequent substrate molecule
*because the activity of allosteric enzymes can very greatly with small changes in substrate concentration
describe how allosteric interactions occur between spatially distinct sites
multiple subunits (quaternary structure)
what do many allosteric proteins consist of?
multiple subunits (quaternary structure)
describe the process of co-operativity in binding
Allosteric proteins with multiple subunits show co-operativity in binding, in which changes in binding at one subunit affect the binding of the remaining subunits
what do allosteric enzymes contain and what are they called
a second type of site, called an allosteric site
What do modulators do?
regulate the activity of the enzyme when they bind to the allosteric site
describe the effect the binding of a modulator may have on a protein
the conformation of the changes and this alters the affinity of the active site for the substrate.
what is the effect of a positive modulator?
increase the enzyme’s affinity for the substrate
what is the effect of a negative modulator?
reduce the enzyme’s affinity
what in haemoglobin shows cooperativity?
The binding and release of oxygen
what alters the affinty of the remaining subunits for oxygen?
changes in binding of oxygen at one subunit
describe the influence and physiological importance of temperature and pH on the binding of oxygen
decrease pH/increase temperature=>
lowers the affinity of haemoglobin for oxygen. Binding of oxygen is reduced.
Reduced increased temperature in actively respiring tissue =>
reduce the binding of oxygen to haemoglobin promoting increased oxygen delivery to tissue
what does the addition or removal of phosphate cause?
what is this a common form of?
reversible conformational change in proteins
post-transitional modification
what is the role of protein kinases?
catalyse the transfer of a phosphate group to other proteins
Describe the use of ATP in phosphorylation reactions.
The terminal phosphate of ATP is transferred to specific R groups
describe the role of protein phosphatases
- catalyse the reverse reaction of kinases (they take the phosphate away from a protein)
what does phosphorylation bring about and what does this affect?
give an example
conformational change, which affects the protein’s activity and teh activity of cellular proteins
e.g. enzymes and receptors
how are proteins activated?
some by phosphorylation, some by inhibition
what affect does adding a phosphate group have?
adds negative charges
ionic interactions in the unphosphorylated protein can be disrupted and new ones created
