Lecture 9 - Protein Ligand Interactions Flashcards Preview

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Flashcards in Lecture 9 - Protein Ligand Interactions Deck (33):
0

Hemoglobin transports molecular oxygen from ________ to _________, then transports CO2 from ________ to _________.

Lung to tissue

Tissue to lung

1

What does myoglobin do?

Stores molecular oxygen in tissue

2

How many hemoglobin monomers are there?

4: α1, α2, β1, β2

3

Where is a heme group bound in each polypeptide chain?

Between helix E and F

4

How many amino acid residues are there in a single polypeptide chain of myoglobin?

153

5

Describe the structure of myoglobin

Tertiary structure of 8 right-handed α-helices with a hydrophobic pocket, which forms a protective sheath for a heme group with iron atom in the middle

6

In terms of myoglobin properties, what happens during periods of oxygen depletion?

Oxy-myoglobin releases its bound oxygen which is then used in metabolism

7

True or false? Secondary structure of myoglobin is unusual

True

8

True or false? Secondary structure of myoglobin is typical of water soluble globular protein.

False, TERTIARY not secondary

9

The oxygen carried by heme-proteins (both myoglobin and hemoglobin) is bound directly to what??

To the ferrous iron atom of the heme prosthetic group

10

True or false? Fe2+ is tetrahedral coordinated in myoglobin and hemoglobin

FALSE, OCTAHEDRAL not tetrahedral

11

CO binds to free heme how many times better than O2? And how many times better than O2 to hemoglobin?

20,000 times

250 times

12

What is he difference between the binding of O2 and CO to a free heme?

O2 binds to free heme at an angle whereas CO binds to free heme perpendicular to heme plane

13

Describe the structure of hemoglobin

Tetramer of four polypeptide chains
Two identical α chains (141 AA residues) and two identical β chains (146 AA residues)
Each chain has a heme group, hence four O2 can bind to each Hb

14

How many identical AA residues do the three polypeptide chains of Mb, α-Hb, and β-Hb have?

27

15

A protein in which the binding of a ligand at one binding site affects the binding properties of another site in the same protein

Allosteric protein

16

True or false? When the first O2 molecule binds to the first subunit of completely deoxygenated hemoglobin, this binding decreases the affinity of the remaining hemoglobin subunits for O2.

FALSE, it INCREASES the affinity

17

True or false? As additional O2 is bound to the second and third subunits of hemoglobin, O2 binding is further strengthened, incrementally

TRUE

18

Monomeric myoglobin has how many O2 binding affinity?

Only ONE

19

The α1-β1 (and α2-β2) interface involves more than ____ residues, but the α1-β2 (and α2-β1) involve only ____ residues

30
19

20

What is the tense (T) state?

The tertiary configuration of low affinity, deoxygenated hemoglobin

21

What is the relaxed (R) state?

The quaternary structure of the fully oxygenated high affinity form of hemoglobin

22

What is the difference between the curve of oxygen binding to myoglobin versus the oxygen binding to hemoglobin?

O2 binding to myoglobin is linear
O2 binding to hemoglobin has 3 phases: hemoglobin, Hb high affinity state, and Hb low affinity state

23

Where does the CO2 bind to deoxy-Hb?

At the amino-terminal end of each globin chain

24

Deoxy-Hb carries CO2 to the _______ and H+ to the _________

Lungs
Kidneys

25

What converts CO2 to HCO3- ?

Carbonic anhydrase

26

What is the sea level BPG?

5 mM

27

What is the BPG at high altitudes?

8 mM

28

True or false? In sickle cell anemia, a single amino acid residue on the surface of the β chain at position 6 is mutated

True, mutated from Glu-6 to Val-6

29

True or false? In sickle cell anemia, position 6 mutation creates a "sticky" hydrophobic contact point on the outside of the β chain

True

30

An immune system anti-body protein in blood serum

Immunoglobin G (IgG)

31

How many antigen binding sites (Fab) does immunoglobin G have?

2

32

The binding specificity of the antibody is determined by what?

The AA's in the variable domains of the light and heavy polypeptide chains