BIOC*3560 - Part A, Regulation of Protein Function

A ______ is a molecule that is permanently

associated with a protein and required for its function. This is considered a _____ interaction.

• ligand, stable

• prosthetic group, stable

• ligand, transient

• prosthetic group, transient

In sickle cell anemia, Hemoglobin S (HbS) is formed due to a single amino acid substitution in which _____ on the ___-globin is changed to _____.

Type answer as ABC X(Y)1, alpha or beta, banana (name the amino acid)

________ mediates the reaction converting ___ to ___ in the ____, decreasing the pH.

Answer explanation

Recall decreasing the pH makes the tissues more acidic.

What are the two reasons why the affinity of CO to bind to heme decreases when heme is bound in an oxygen-binding protein such as Myoglobin or Hemoglobin?

Answer explanation

Steric hindrance between His E7 & CO decreases affinity of heme for CO as CO binds straight and kind of bumps into the distal histidine.

Oxygen also binds at an angle creating a favourable bond

What does K_d represent? Provide its formula and units as well.

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Answer explanation

K_d is the dissociation constant and represents the ligand concentration, [L] at which half of the ligand-binding

sites are occupied. Its units are in concentration (e.g., g/L, molar [M], etc.)

K_d represents when Θ (occupancy) = 0.5

What does Θ (theta) represent? Provide its formula and units as well.

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Answer explanation

Occupancy is typically expressed as a ratio and not a percentage!

Occupancy is expressed in terms of variables that WE can manipulate – experimentally ligand concentration is usually altered.

A(n) _______ is the region of a protein surface that interacts with a ligand.

Answer explanation

When a conformational change occurs that makes the binding site of a protein more complementary to the ligand, this creates a(n) ________.

Answer explanation

Match the image to the kind of protein structure

• Backbone & ribbon

• 
• Surface charge

• 
• Space filling

• 
• Wireframe

• 

Match the description to the kind of protein structure

• Surface charge

• Indicates alpha helices and beta strands

• Wireframe

• Blue = positive

  Red = negative

• Backbone & ribbon

• Each atom is represented by one sphere

• Space filling

• Lines represent covalent bonds between atoms

Answer explanation