The Structure of Cyclooxygenase-1 with Bound Arachidonic Acid

See the structure of aspirin

See the amino acid structure of Cox-1


CPK Color Scheme

C O N Co3+

This is the human cyclooxygenase-1 protein (Cox-1). Cox-1 is colored to show alpha helices in red ribbons, and beta-pleated sheets in yellow ribbons.
Click here to reset the view of Cox-1.

If you zoom in some, you will see arachidonic acid (gray structure surrounded with dots made of mostly carbon and hydrogen) that is bound inside the active site of Cox-1. The two red atoms on arachidonic acid are oxygen.

Notice the protoporphyrin IX ring with Cobalt 3+ ion in the center .

Zoom Out and examine it yourself .
Locate Serine #530 that is acetylated by aspirin. Aspirin adds an acetyl group to Serine 530 which as you can see is very near the arachidonic acid. Acetylation of Cox-1 (or Cox-2) irreversibly inactivates the enzyme. That's how aspirin works.