7. Primary Pumps Flashcards
what are the 4 types of different ATP powered pumps
P-type ATPases
V-type proton pump
F-type proton pump
ABC superfamily
what ions do P-type ATPases pump
cations: K+, Na+, Ca2+, H+, Mg2+
what inhibits P-type ATPases - how?
orthovanadate
- prevents phosphorylation events
how do P-type ATPases work
during ATP hydrolysis: ATP donates its gamma phosphate to a conserved aspartate - forming a phosphorylated intermediate
sodium-potassium pump:
where is it found?
substrates?
structure?
in eukaryotic plasma membranes
3Na+ out to 2K+ in per ATP molecule hydrolysed
2 alpha subunits regulated by 2 beta subunits
what is an inhibitor of a sodium potassium pump
ouabain
fungal and plant H+ ATPase:
where is it found?
substrates?
structure?
- plasma membranes of plant and fungal cells
- 1 H+ per ATP hydrolysed
- composed of 1 alpha subunit
what is the function of sodium-potassium pumps
maintains high K+ and low Na+ in the cytosol
- maintaining Na+ electrochemical potential
If there is no ….., the sodium potassium pump won’t work
potassium
what is the function of plant and fungal H+ ATPase pump
expel excess hydrogen produced during metabolism
- generating an electrochemical gradient
- regulating cytosolic pH
sarcoplasmic end-reticulum Ca2+ ATPase:
- location?
- substrates?
- structure?
sarcoplasmic reticulum of muscle cells
2Ca2+ per ATP molecule
1 alpha subunit (3 isoforms)
what is the function of sarcoplasmic endoreticulum Ca2+ ATPase
restores low cytosolic calcium following muscle contraction
what does SERCA stand for?
sarcoplasmic endoreticulum Ca2+ ATPase
gastric mucosal H+/K+ ATPase:
- location
- substrates
- structure
plasma membrane of gastric epithelium cells
2H+ to 2K+ per ATP molecule hydrolysed
2 alpha and 2 beta subunits
what is the function of gastric mucosal H+/K+ ATPase
H+ secretion into the lumen of the stomach - acidic stomach
where are plasma membrane calcium ATPase pumps found
fungal, plant and animal plasma membranes
what is the function of plasma membrane calcium ATPase
maintains low cytosolic calcium, central role in cell signalling
how does the plasma membrane Ca2+ ATPase work
1-2 Calcium’s per ATP, in exchange for a H+
describe the structure of the N and C-terminus regions on a P-type ATPase
N-terminus = 4 TMS
C- terminus = 6 TMS
where is the majority of the P-type ATPase pump located
in the cytoplasm (hydrophilic region)
describe the E1-E2 model of P-type pumps
- E1 = binding site has low affinity for K+, so only binds sodium
- E1 conformationally changes into E2 = binding site now faces OUTSIDE the membrane
- when in E2 = low affinity for Na+, high affinity for K+, sodium dissociates allowing K+ to bind
- E2 converts back into E1 (via conformational change) = inward transport of K+
what does the conformational change P-type pumps undergo allow?
allows the cell to bind ions at low concentrations, and dissociate ions at high concentrations
what facilitates the conformational change, moving E1 to E2?
ATP hydrolysis donates gamma phosphate to aspartate
= phosphorylation of aspartate moves the head regions
= conformational change
what molecules do CPx type pumps transport
toxic and nutrient metals: e.g. Cu, Pb, Cd and Zn
name a species was first identified as having CPx type pumps
enterococcus
what is Menkes disease
mutations to CPx type pumps causing systemic copper deficiency
name 2 key differences between CPx type pumps and P-type pumps
CPx =
N-terminus has 2 extra TMS domains
c-terminus has fewer TMS domains
what is the CPx motif
C = cysteine P = proline X = cysteine or histidine or serine
from an archetype ATPase, what two classes of pumps emerged
one for heavy metals - CPx type
one for other cations - P-type
what do V-type pumps target exclusively
protons (H+)
what organisms have V-type pumps
eukaryotes (intracellular membranes)
what is rotational catalysis
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
what are ABC binding cassette transporters involved in
using energy from ATP hydrolysis to transport a variety of solutes in or out of the cell
where does the substrate bind in ABC transporters
chamber
what is the mechanism of action for ABC transporters
- the lipid soluble molecule dissolves into the plasma membrane and binds to MDR1 protein chamber
- powered by ATP hydrolysis, the substrate is flipped into the exoplasmic section of the plasma membrane
- the substrate molecule diffuses into the extracellular space
