Genetic engineering of the heme pocket in human serum albumin: modulation of [O.sub.2] binding of iron protoporphyrin IX by variation of distal amino acids

The additional new mutations designed for manipulating the architecture of heme pocket in recombinant human serum albumin (rHSA)-heme complexes by altering distal amino acids are described. The replacement of polar Arg-186 with Leu or Phe has increased the hydrophobicity of the distal environment, has yielded a complex with reduced [O.sub.2] binding affinity, which is almost the same as that of human red blood cells and therefore better tuned to a role in [O.sub.2] transport.