Molecule of the Month: Nitric Oxide Synthase
Nitric oxide gas is used as a rapid-acting hormone and as a powerful defense
Exploring the Structure
Nitric Oxide Synthase (PDB entries 1nod, 2nse, 1om4 and 3e7t)
The three forms of NOS are very similar, but researchers are taking advantage of small differences to create drugs to block one, but not the others. This would be very useful: for instance, the inducible NOS plays a role in Parkinson's disease, Alzheimer's disease and multiple sclerosis, so a drug that blocks it, but not the other forms of NOS, could be used to help treat these diseases. Unfortunately, the active sites of the three forms are almost identical, so researchers have been forced to design larger drugs that reach into areas that show differences. To compare the structures of the catalytic domain of inducible NOS (PDB entry 1nod ), endothelial NOS (PDB entry 2nse ), neuronal NOS (PDB entry 1om4 ), and NOS with an inhibitor bound in the active site (PDB entry 3e7t ), click on the image for an interactive Jmol.
Topics for Further Discussion
- Nitric oxide synthase is also made in some bacteria. You can compare the structures of the bacterial enzymes with the mammalian enzymes using the "Structure Comparison" tool at the PDB.
- Many structures of trial drugs bound to nitric oxide synthase are available in the PDB. You can use the "Ligand Explorer" to examine the interaction of these drugs with the enzyme and enzyme cofactors.
January 2011, David Goodselldoi:10.2210/rcsb_pdb/mom_2011_1