Nitric oxide is attached to a conserved cysteine in hemoglobin and then released to control the flow of blood.
Signaling with NO
Exploring the Structure
The structure of S-nitrosylated hemoglobin (PDB entry 1buw) was determined by starting with crystals of hemoglobin with carbon monoxide, and then exposing them to nitric oxide gas. Since the carbon-monoxide-bound form has a similar structure as oxygenated hemoglobin, only small changes occurred when nitric oxide attached: two amino acids at the end of the chain (numbers 145 and 146) became disordered. To explore the structures of S-nitrosylated and carbonmonoxy hemoglobin (PDB entry 1hco), click on the image for an interactive JSmol.
Topics for Further Discussion
- Myoglobin in some cold-blooded animals is also regulated by nitric oxide. Take a look at PDB entry 2nrm to see S-nitrosylated myoglobin from tuna.
- The PDB archive includes many other S-nitrosylated proteins. Look at the list included on the ligand page for SNC (S-nitroso-cysteine).
May 2019, David Goodselldoi:10.2210/rcsb_pdb/mom_2019_5