Recombinant Single Globin-Chain Expression and Purification

The development of molecular biological techniques to selectively replace individual amino acids has furthered our understanding of the relationship between the structure and function of hemoglobin (Hb). Initial reports described production of normal and modified human globin chains in bacteria employing a fusion-protein expression vector (1 ). An expression system was later developed in which α- and β-globin chains were coexpressed, resulting in the formation of soluble tetrameric Hb in yeast (2 ,3 ). Coexpression of human α and β globin in Escherichia coli that resulted in the formation of soluble tetrameric Hbs was described (4 ), as well as a system for high expression of insoluble β-globin chains in E. coli. (5 ). These last two systems, however, result in globin chains containing an N-terminal methionine that may affect the functional properties of Hb. In 1993, Shen et al. (6 ) expressed soluble Hb tetramers lacking the N-terminal methionine in bacteria by coexpression of α- and β-globin cDNAs with methionine aminopeptidase (MAP) cDNA.