Acetylcholine receptor channel imaged in the open state

Area of Science:

• Structural biology
• Neuroscience
• Biochemistry

Background:

• The acetylcholine receptor (AChR) is a key neurotransmitter receptor crucial for synaptic transmission.
• Understanding the structural dynamics of AChR gating is vital for comprehending neuronal signaling.

Purpose of the Study:

• To determine the structure of the open-channel form of the acetylcholine receptor.
• To elucidate the mechanism by which acetylcholine binding triggers channel opening.

Main Methods:

• Electron imaging of Torpedo ray postsynaptic membranes.
• Cryo-electron microscopy (cryo-EM) to visualize receptor structures.
• Rapid mixing techniques to capture transient open states.

Main Results:

• The open-channel structure of the acetylcholine receptor was resolved.
• Acetylcholine binding induces small subunit rotations in the extracellular domain.
• These rotations trigger conformational changes in the pore-lining alpha-helices, opening the channel.
• The open pore exhibits a tapering shape towards the intracellular side, formed by a twisted helical barrel.

Conclusions:

• The study reveals the precise structural mechanism of acetylcholine receptor channel gating.
• Subunit rotation and pore helix rearrangement are critical steps in channel activation.
• The findings provide atomic-level insights into neurotransmitter receptor function.