Lecture Notes: ATP Synthase Structure in Electron Transport Chain

Introduction

Electron transport chain: Functions to move electrons across the inner mitochondrial membrane.
Proton electrochemical gradient: Established across the inner membrane.
ATP synthase (Complex 5): Uses proton motive force to synthesize and release ATP into the mitochondrial matrix.

Location: Inner membrane of the mitochondria.
Two main regions:
- F₀ region: Proton channel
- F₁ region: Catalytic unit

Role: Binds ADP and phosphate to form ATP.
Structure: Lies in the mitochondrial matrix.
Polypeptide chains:
- Alpha (dark green)
- Beta (light green)
- Gamma (red)
- Epsilon (blue)
- Delta (purple)
Alpha and Beta units:
- 3 individual Alpha units
- 3 individual Beta units
- Form a hexameric alpha₃ beta₃ ring structure
- Function:
  - Alpha units can bind ATP
  - Beta units synthesize and release ATP
- Hexameric ring catalyzes ATP synthesis

Function: Form the central stalk
Central stalk:
- Elongated structure through the inner cavity of the hexameric ring
- Connects to the F₀ region
Role: Rotates to stimulate ATP synthesis and release

Role: Allows proton movement
Location: Hydrophobic, lies within the inner mitochondrial membrane.
Components:
- C units:
  - 10 to 14 subunits
  - Form ring structure, acts as proton channel
- A unit:
  - Lies on outer portion of C ring
  - Assists in proton transport
  - Connects C ring to F₁ unit

Two connection points:
- Gamma-Epsilon central stalk
- Arm formed by A subunit, 2 B units, and Delta unit

Rotating region:
- C ring and Gamma-Epsilon central stalk
Stationary region:
- A unit, 2 B units, Delta unit, Alpha and Beta units
In upcoming lectures: Mechanism of ATP synthase and proton movement to synthesize ATP.