Haemoglobin
structure
- HbA = a2 b2 = the population average
- HbA2 = a2 delta 2
- HbF = a2 gamma 2
basically has an openable hydrophobic pocket
Sickle cell disease is caused by a point mutation in the sixth codon of beta-globin that leads to the replacement of a glutamate residue with a valine residue (Robbins)
special features which you probably don't need to know
- essentially good transporter for small molecules due to shape and binding sites
- iron ion in haem can go between 2+ and 3+ → participate in redox reactions!
function
- Oxygen transport (affinity described by the oxygen dissociation curve)
- CO2 transport
- NO scavenging (NO binds to ferric ion) → contributes to regional autoregulation! Quoted clinical examples:
- Hypoxic pulmonary vasoconstriction, and the pulmonary hypertension seen with polycythaemia (Deem, 2004).
- Sickle cell vasoconstrictive crisis (Mack & Kato, 2004)
- Buffering? (histidine groups)
breakdown
(via haem oxygenase) bilverdin → (biliverdin reductase) bilirubin (See Bilirubin metabolism)
🏠 hepatocytes