Lecture 2.2: Soluble Transport Proteins

Question 1

Myoglobin is a good oxygen [–] protein

Answer 1

storage

Question 2

Sigmoidal O2 binding patterns

Answer 2

sigmoidal curve = oxygen is a good TRANSPORTER
higher pO2 = loading of O2
lower pO2 = release of O2

Question 3

When O2 is unbound what is the conformation of heme?

Answer 3

DeoxyHb = puckered heme

Question 4

when O2 is bound what is the conformation of heme?

Answer 4

OxyHb = planar heme

Question 5

When O2 is bound what happens to the conformation of His F8 and F helix

Answer 5

the His F8 and F helix move towards the heme, resulting in tertiary structure

Question 6

T-state trends

Answer 6

tense = deoxyhemoglobin = unbound form = low affinity for O2

Question 7

R-state trends

Answer 7

relaxed = oxyhemoglobin = bound form = high affinity for O2

Question 8

A hydrogen bond between [–] and [–] stabilizes the T-state?

Answer 8

Asp99 carboxylic group and Tyr42 hydroxyl group

Question 9

A hydrogen bond between [–] and [–] results in R-state stabilization?

Answer 9

Asp94 carboxylic group and Asn102 amino group

Question 10

Concerted Model

Little to no ligand is bound

Answer 10

T-state favored

Question 11

Concerted Model

ligand binding shifts the entirew tetramer simultaneously from [–] to [–]

Answer 11

T to R

Question 12

Concerted Model

Binding of ligand [increases or decreases] the population of [–] state

Answer 12

increases, R

Question 13

Concerted or Sequential Model

The last O2 binds with [–]x [–] affinity than the first

Answer 13

100x higher

FULLY OXYGENATED

Question 14

Sequential Model

Ligand binding to one subunit induces conformation change of [–] subunit to the [–] state

Answer 14

adjacent, R

Question 15

Sequential Model

Two states can exist in the [–] tetramer

Answer 15

same

Question 16

Steps for O2 cooperativity

Answer 16

1. O2 binds to first tetramer
2. Fe2+ moves into heme
3. F-helix (his) shifts
4. bonds rearrange at interfaces
5. fully saturated

Question 17

how can affinity for O2 change?

Answer 17

• Protein has multiple ligand sites
• binding of effector molecules induces conformational change
• conformational changes are translated to neighboring ligand binding sites, influencing their affinity for ligand
• protein shifts between two conformations: high and low affinity

Question 18

cooperativity is recognized by what type of curve?

Answer 18

sigmoidal

Question 19

if the hill coefficent is >1 what us the cooperativity?

Answer 19

positive

Question 20

if the hill cofficient is <1 what is the cooperativity?

Answer 20

negative

Question 21

if the hill coefficent is =1 what is the cooperativity?

Answer 21

none

Question 22

positive cooperativity

Answer 22

the first binding increases the affinity of the second site

(hemoglobin)

Question 23

negative cooperativity

Answer 23

the first binding event decreases the affinity for the second site

Question 24

no cooperativity

Answer 24

myoglobin

Question 25

Heterotropic/ Allostery

Answer 25

Effector binds to secondary sites & influences binding of the ligand at the primary site

Question 26

Homotropic/Cooperativity

Answer 26

ligand binds to one site & influences binding of the same ligand at a different site

Question 27

What happens to the o2 saturation curve when in high temps?

Answer 27

shifts right = decreased affinity

Question 28

what happens to the O2 saturation curve when in low temps

Answer 28

shifts left = increased affinity

Question 29

Three ways to remove CO2

Answer 29

1. dissolved CO2 gas
2. dissolved bicarbonate (80-85%)
3. bound to hemoglobin

Question 30

Low pH favors [–] state and [–] O2 affinity

Answer 30

T, decreases

Question 31

H+ is a [–] effector

Answer 31

heterotropic allosteric

Question 32

increased H+ = [–] pH = [–] binding affinity

Answer 32

decreased pH, low binding affinity

Question 33

How does bicarbonate stabilize T-state

Answer 33

binds to the N-termini of Hb subunits

Question 34

carbamylating further [–] and produces and additional [–] in O2 saturation of Hb

Answer 34

stabalizes the T-state, decrease

Question 35

CO2 is a [–] effector

Answer 35

negative heterotropic allosteric effector

Question 36

2,3 BPG interacts with?

Answer 36

K, R, H

lysine, arginine, histadine

2,3 BPG is negatively charged

Question 37

2,3 BPG is a [–] effector

Answer 37

negative heterotropic allosteric effector

Question 38

When 2,3 BPG levels are normal what is the difference in fractional saturation in the lungs?

Answer 38

33%

Question 39

When 2,3 BPG levels are elevated what is the difference in fractional saturation in the lungs?

Answer 39

~40%

Question 40

Slow Metabolic Rate Trends

Answer 40

decrease temp = decrease CO2 = increase pH = decrease 2,3 BPG

Question 41

Fast Metabolic Rate

Answer 41

increased temp = increased CO2 = decreased pH = increased 2,3 BPG