1.23 b) Ligand Binding Changes the Conformation of a Protein Flashcards
What is a ligand?
A substance which can bind to a protein
Under what circumstances does the conformation of a protein change?
if a ligand binds to a protein’s binding site (eg a substrate binds to an enzyme’s active site)
Conformational changes in proteins causes ___ changes.
functional
R groups not involved in protein folding can allow ___ to ligands.
binding
Binding sites have a complementary ___ and ___ to the ligand.
shape, chemistry
Induced fit is a ___ change in the shape of the ___ site, which increases the ___ interacting with the substrate.
temporary, active, area
This chemical environment lowers the ___ ___ for the reaction.
activation energy
Name the two sites that allosteric enzymes have.
active site and allosteric site
Allosteric enzymes can change ___ upon binding a ___.
conformation, modulator
In allosteric enzymes, modulators bind at secondary locations known as ___ ___.
allosteric sites
Once the modulator has bound, the conformation of the enzyme changes which alters the ___ of the ___ ___.
shape, active site
Modulators that increase the enzyme’s affinity for the substrate are called…
positive modulators
Modulators that decrease the enzyme’s affinity for the substrate are called…
negative modulators
Modulators bind to the ___ ___ and change the shape of the ___ ___.
allosteric site, active site
What is cooperativity?
when a ligand binding to one subunit of a multi-subunit protein changes the affinity of the other subunits for that ligand
In what type of proteins does cooperativity occur?
ones with quarternary structure
What is an example of a molecule that exhibits cooperativity?
haemoglobin
Haemoglobin has quarternary structure and so is made of 4 ___ ___.
Each one has a ___ group, capable of binding to a molecule of ___.
polypeptide chains.
haem, oxygen
When one of haemoglobin’s subunits binds an oxygen molecule the remaining subunits bind with ___ ___.
increasing ease
The reverse is also true, when the first of oxy-haemoglobin’s subunits releases its oxygen molecule, the remaining subunits release theirs with ___ ___.
increasing ease
What are the two main factors that affect haemoglobin’s affinity to oxygen?
pH and temperature
Describe how haemoglobin’s affinity to oxygen changes under the following conditions:
1. As temperature increases
2. As pH increases
- affinity decreases.
- affinity increases
Describe the conditions in actively respiring tissue with respect to temperature and pH and; suggest a benefit to these conditions.
Actively respiring tissue has a high temperature and low pH;
this lowers haemoglobin’s affinity to oxygen, which promotes oxygen delivery to respiring cells (which require oxygen)
Phosphates can cause ___ conformational changes in proteins.
reversible
The addition of phosphate groups is a common form of __-__ ___.
post-translational modification
What is the name of the enzyme that catalyses the addition of phosphate groups to other proteins?
protein kinase
The phosphate group that is transferred by the enzyme ___ ___, comes from ___ (it is the ___ phosphate).
protein kinase, ATP, terminal/third
What is the name of the enzyme that catalyses the reverse reaction (dephosphorylation)?
protein phosphatase
Phosphorylation affects a proteins activity by causing ___ ___.
conformational changes
Proteins can be ___ or ___ by phosphorylation. This is how many cellular proteins are ___.
activated, inhibited.
regulated
Phosphate groups have a ___ charge (just like phosphorus ions haha cute)
negative
Since phosphate groups have a negative charge, phosphorylation can disrupt the ___ interactions in the un____ protein, or create new ones.
ionic, unphosphorylated
Name a protein who’s function is dependent on phosphorylation.
The sodium potassium pump (its phosphorylated by ATP to transport 3 sodiums out and dephosphorylated by ADP to transport 2 potassiums in)
