Data obtained during RapiData 2008 were used to probe structural and functional properties of human hemoglobin by Jun Yi from the group of George Richter-Addo at the University of Oklahoma

Jun Yi

Structure and function of the human hemoglobin•nitrite complex

Yi, J., and Richter-Addo, G.
University of Oklahoma Department of Chemistry and Biochemistry

Hemoglobin needs to be in a reducd state to transport oxygen. Therefore it is a heme-Fe(II) center within hemoglobin (Hb) that binds and transports oxygen throughout the body. Nitrite (NO₂^-) is a ubiquitous simple anion present in the environment and as a food additive. The Hb-nitrite chemistry and physiology are known to be complex. For example, nitrite also oxidizes the heme-iron center of Hb to its inactive ferric state, and to promote hemoglobin degradation, both of which impair oxygen transport. Thus, accidental nitrite poisoning leads to symptoms of dizziness, loss of consciousness, or even death. Surprisingly, no structural information has been previously reported for a Hb•nitrite complex. We determined the structure of the Fe(III)•NO₂ Hb complex to 1.8 Å resolution for the first time. Our structure reveals that the nitrite ligand adopts an uncommon Fe-O-N-O binding mode and appears to induce disorder of the beta subunit heme group. Our correlated single crystal spectroscopic and crystallographic analysis performed at NSLS beamline X26-C is continuing to provide an experimental and an intellectual framework for a more complete understanding of the physiological interactions between the nitrite and Hb.

The Nitrite Anion Binds to Human Hemoglobin via the Uncommon O-Nitrito Mode
Jun Yi, Martin K. Safo, and George B. Richter-Addo
Biochemistry, (2008) 47: 8247-8249