Myoglobin (Mb) and hemoglobin (Hb) have very similar roles in that both proteins bind oxygen.  The heme-bound oxygen is stabilized through hydrogen bonding from the distal protonated histidine.  We have recently used fluoride ion in our research to understand the role of the distal histidine in the ferric state of heme proteins.  Our study at various pH shows that the heme-bound protein to heme loss transitions in ferric Mb and Hb occur at a pKa of 4.5.  However, in the presence of fluoride ion, the heme loss transitions in both of these proteins are shifted to a pKa of 4.2.  This shows that the heme-bound fluoride stabilizes the ferric state by being a better hydrogen acceptor than the water ligand.

Heme loss in myoglobin and hemoglobin in the presence of fluoride

245th National Meeting (2013)

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