The properties and interactions of the isolated α and β chains of human haemoglobin : I. Sedimentation and electrophoretic behaviour

Abstract

The α and β chains of human haemoglobin A 1 may be isolated by starch block electrophoresis or by chromatography after treatment of the protein with p -mercuribenzoate. The chains so isolated do not show any free SH groups; however, after treatment with cysteine or thioglycolate, between 1 and 2 SH groups per β chain and 1 per α chain become titratable. The chains before and after such treatment are designated α PMB† or β PMB and α SH or β SH respectively. Ultracentrifugal analysis shows that the isolated α SH and α PMB chains are both monomeric; in contrast the β PMB chains tend to polymerize. The β SH chains are heterogeneous but the major component appears to be a tetramer and may be identified with haemoglobin H. A mixture of α PMB and β PMB chains in equal amounts is homogeneous and has a sedimentation coefficient in the neighbourhood of 3. A similar mixture of α SH and β SH chains behaves like haemoglobin A both in the ultracentrifuge and in starch gel electrophoresis. Certain systems which are homogeneous in the centrifuge and on Sephadex show multiple bands in electrophoresis, which implies differences beyond those due to molecular weight. These results are discussed in terms of the interactions between the chains under various conditions.