FUNCTIONS OF

PLASMA MEMBRANE

PRESENTED BY:

DR.SAPNA KUMARI

ZOO CC – 204

SEMESTER – II

UNIT- 2

E1 - high affinity for Ca2+, 2 Ca2+ bound, 2 H+ counter ions released.

E1⋅2Ca2+ - cytoplasmic gate open, free Ca2+ ion exchange occurs between bound ions and those

in cytoplasm, closed configuration of N, P, A domains broken, exposing catalytic site.

E1⋅ ATP - ATP binds and links N to P, P bends, N contacts A, A causes M1 helix to pull up, closes

cytoplasmic gate, bound Ca2+ occluded in transmembrane

E1⋅ADP - Phosphoryl transfer, ADP dissociates

E1P - A rotates, transmembrane helices rearrange, binding sites destroyed, lumenal gate opened,

bound Ca2+ released

E2P - open ion pathway to lumen, Ca2+ to lumen

E2⋅Pi - A catalyzes release of the Pi, P unbends, transmembrane helices rearranged, closes

lumenal gate

E2 - transmembrane M1 forms cytoplasmic access tunnel to Ca2+ binding sites