7. Primary Pumps

Question 1

what are the 4 types of different ATP powered pumps

Answer 1

P-type ATPases
V-type proton pump
F-type proton pump
ABC superfamily

Question 2

what ions do P-type ATPases pump

Answer 2

cations: K+, Na+, Ca2+, H+, Mg2+

Question 3

what inhibits P-type ATPases - how?

Answer 3

orthovanadate

- prevents phosphorylation events

Question 4

how do P-type ATPases work

Answer 4

during ATP hydrolysis: ATP donates its gamma phosphate to a conserved aspartate - forming a phosphorylated intermediate

Question 5

sodium-potassium pump:
where is it found?
substrates?
structure?

Answer 5

in eukaryotic plasma membranes
3Na+ out to 2K+ in per ATP molecule hydrolysed
2 alpha subunits regulated by 2 beta subunits

Question 6

what is an inhibitor of a sodium potassium pump

Answer 6

ouabain

Question 7

fungal and plant H+ ATPase:
where is it found?
substrates?
structure?

Answer 7

• plasma membranes of plant and fungal cells
• 1 H+ per ATP hydrolysed
• composed of 1 alpha subunit

Question 8

what is the function of sodium-potassium pumps

Answer 8

maintains high K+ and low Na+ in the cytosol

- maintaining Na+ electrochemical potential

Question 9

If there is no ….., the sodium potassium pump won’t work

Answer 9

potassium

Question 10

what is the function of plant and fungal H+ ATPase pump

Answer 10

expel excess hydrogen produced during metabolism

• generating an electrochemical gradient
• regulating cytosolic pH

Question 11

sarcoplasmic end-reticulum Ca2+ ATPase:

• location?
• substrates?
• structure?

Answer 11

sarcoplasmic reticulum of muscle cells

2Ca2+ per ATP molecule

1 alpha subunit (3 isoforms)

Question 12

what is the function of sarcoplasmic endoreticulum Ca2+ ATPase

Answer 12

restores low cytosolic calcium following muscle contraction

Question 13

what does SERCA stand for?

Answer 13

sarcoplasmic endoreticulum Ca2+ ATPase

Question 14

gastric mucosal H+/K+ ATPase:

• location
• substrates
• structure

Answer 14

plasma membrane of gastric epithelium cells

2H+ to 2K+ per ATP molecule hydrolysed

2 alpha and 2 beta subunits

Question 15

what is the function of gastric mucosal H+/K+ ATPase

Answer 15

H+ secretion into the lumen of the stomach - acidic stomach

Question 16

where are plasma membrane calcium ATPase pumps found

Answer 16

fungal, plant and animal plasma membranes

Question 17

what is the function of plasma membrane calcium ATPase

Answer 17

maintains low cytosolic calcium, central role in cell signalling

Question 18

how does the plasma membrane Ca2+ ATPase work

Answer 18

1-2 Calcium’s per ATP, in exchange for a H+

Question 19

describe the structure of the N and C-terminus regions on a P-type ATPase

Answer 19

N-terminus = 4 TMS

C- terminus = 6 TMS

Question 20

where is the majority of the P-type ATPase pump located

Answer 20

in the cytoplasm (hydrophilic region)

Question 21

describe the E1-E2 model of P-type pumps

Answer 21

1. E1 = binding site has low affinity for K+, so only binds sodium
2. E1 conformationally changes into E2 = binding site now faces OUTSIDE the membrane
3. when in E2 = low affinity for Na+, high affinity for K+, sodium dissociates allowing K+ to bind
4. E2 converts back into E1 (via conformational change) = inward transport of K+

Question 22

what does the conformational change P-type pumps undergo allow?

Answer 22

allows the cell to bind ions at low concentrations, and dissociate ions at high concentrations

Question 23

what facilitates the conformational change, moving E1 to E2?

Answer 23

ATP hydrolysis donates gamma phosphate to aspartate

= phosphorylation of aspartate moves the head regions

= conformational change

Question 24

what molecules do CPx type pumps transport

Answer 24

toxic and nutrient metals: e.g. Cu, Pb, Cd and Zn

Question 25

name a species was first identified as having CPx type pumps

Answer 25

enterococcus

Question 26

what is Menkes disease

Answer 26

mutations to CPx type pumps causing systemic copper deficiency

Question 27

name 2 key differences between CPx type pumps and P-type pumps

Answer 27

CPx = N-terminus has 2 extra TMS domains c-terminus has fewer TMS domains

Question 28

what is the CPx motif

Answer 28

``` C = cysteine P = proline X = cysteine or histidine or serine ```

Question 29

from an archetype ATPase, what two classes of pumps emerged

Answer 29

one for heavy metals - CPx type one for other cations - P-type

Question 30

what do V-type pumps target exclusively

Answer 30

protons (H+)

Question 31

what organisms have V-type pumps

Answer 31

eukaryotes (intracellular membranes)

Question 32

what is rotational catalysis

Answer 32

ATP hydrolysis by A-B complex generates the torque in the D subunit to rotate the ring of C subunits - which is where protons bind

Question 33

what are ABC binding cassette transporters involved in

Answer 33

using energy from ATP hydrolysis to transport a variety of solutes in or out of the cell

Question 34

where does the substrate bind in ABC transporters

Answer 34

chamber

Question 35

what is the mechanism of action for ABC transporters

Answer 35

1. the lipid soluble molecule dissolves into the plasma membrane and binds to MDR1 protein chamber 2. powered by ATP hydrolysis, the substrate is flipped into the exoplasmic section of the plasma membrane 3. the substrate molecule diffuses into the extracellular space