Types of ATPases

Question 1

What type of ATP ase is the Na/K pump and how much of a cell’s energy is expended on it?

Answer 1

P, 1/2

Question 2

Draw it working

Answer 2

see notes

Question 3

In plant and fungal cells what P-type ATPase predominates and how big is it?
How much of the cell’s ATP supply does it consume?

Answer 3

H+ translocator, 100kDa polypeptide, also consumes half the cell’s ATP supply, creates large inside membrane voltage and pH gradient (H+ pumped out)

Question 4

What are V-type ATPases?

Answer 4

Largely H+ translocating pumps found in endomembranes like vacuoles

Question 5

Describe V-type

Answer 5

Driven by hydrolysis of cytosolic ATP, multi subunit with integral V0 (250 kDa) domain and peripheral V1 (500kDa) domain
Now known to function as a rotory motor

Question 6

When Vtype ATPase fails…

Answer 6

Found to lead to cancer

Question 7

Draw diagram of uniport, symport and antiport

Answer 7

see notes

Question 8

Draw how Na+ coupled glucose transport works in gut

Answer 8

see notes

Question 9

Draw F type ATPase

Answer 9

see notes

Question 10

How does F type ATPase work?

Answer 10

1) H+ enter F0 domain at c-a subunit interface
2) H+ sequential binding and release at weakly acidic residues changes electrostatic interactions in the domain resulting in rotation
3) Torque is transmitted to F1 domain via rotation of gamma-epsilon shaft
4) As camshaft goes through 120 degree rotation change in alpha-beta subunit conformation releases ATP

Question 11

How can rotation of F type ATPase be shown?

Answer 11

Beta units of stator anchored via His tag to surface of tiny Nickel-covered beads (coat microscope slide)
Camshaft (gamma and epsilon) attached to fluorescent actin filament
Rotor driven artificially by adding ATP and rotation of actin viewed with fluorescent microscope