Haemoglobin

Protein contains four subunits designated to α and β. Each subunit contains a haem group that binds reversibly with O₂.

The nine highly conserved amino acid residues in haemoglobin are given in Table 3.1.

Table 3.1 Highly Conserved Amino Acid Residues in Haemoglobin

Position	Amino acid	Role
F₈	Histidine	Proximal haem-linked histidine
E₇	Histidine	Distal haem-linked histidine
CD₁	Phenylalanine	Haem contact
F₄	Leucine	Haem contact
B₆	Glycine	Allows close approach between B and E helices
C₂	Proline	Helix formation
HC₂	Tyrosine	Cross links the F and H helices
C₄	Threonine	Uncertain
H₁₀	Lysine	Uncertain