Plant Phys exam 3: 4 ATP synthesis

Describe the structure of ATP synthase

alpha and beta- active site for ATP synthesis

beta- catalytic site

b- prevents alpha and beta from moving

Y- attached to c-ring, Y rotates as C ring rotates… between alpha and beta subunits

c- (c-ring) 8-14 subunits; H+ binding site, rotates 30-36 degrees when binging to C ring

a- H+ movement… H+ entrance from lumen/ H+ exit to stroma

How do protons flow through ATP synthase?

H+ enter and exit ATP Synthase via the a subunit

• H+ binding to C subunits causes rotation of ring (≅ 30-36 degrees)

• C ring rotation causes rotation of 𝛄 subunit

• 𝛄 rotation changes conformational of catalytic site in B subunits and drives the synthesis of ATP

• Head unit does not rotate – its static

• (and held in place by b and 𝜹)

What influence does the H+ concentration have on ATP synthase?

higher concentration= more likely to bind

lower concentration= more likely to dissociate

Which subunit in ATP synthase is variable amongst organisms?

C ring subunit

What is rational catalysis?

For each beta subunit (β) the active site can exists as O (open) L (loose) T (tight) conformations

• Proton flow and rotation of asymmetric gamma subunit changes the conformation

• 3 ATP/360 degree rotation of gamma subunit