Mutations in heme pocket resulting in unstable hemoglobins

Schematic representation of the heme pocket, showing the replacement site of several of the unstable hemoglobins. Valine E4 is at the corner of the pocket; its side chain does not make contact with the heme but does affect the placement of adjacent amino acid side chains.

• Circle with Fe: iron
• Blue structure: heme
• White structure: globin
• Black structures: substituted side chains