Chapter 2: Structural overview

Hattori and Gouaux now had their two structures for comparison. Despite some structural differences, they found that both receptors share the same domains and have the architecture and protein fold characteristic of P2X receptors. You can see this clearly in the image below.

Picture- top view and side view of the closed (apo) P2X receptor:

Picture- Side view and top view of open ATP bound P2X receptor:

We have summarised the key structural features shared by both receptors:


Key structural features

• 3 dolphin shaped subunits
•  Each subunit possesses a large, glycosylated extracellular domain-the ‘body’ of the dolphin and two transmembrane alpha helices- the ‘tail’ or ‘flukes’ of the dolphin.
•   Making more of the dolphin analogy, the extracellular domain of each subunit has been divided by Hattori and Gouaux into a head, upper body, lower body, dorsal fin, right flipper and left flipper:

• The subunits associate to form a chalice-like trimer
• The 6 transmembrane helices form the non-selective cation pore.
•  The extracellular domains are where all the magic happens-containing binding sites for ATP, antagonists and allosteric modulatory metal ions.
•  The extracellular domains have openings that lead into a wide extracellular vestibule.
•  The extracellular vestibule leads into the non-selective cation channel pore which narrows to a gate region.
•  The amino and carboxy termini are thought to be short and intracellular