The oxygen equilibrium of the isolated α and β ohains of human haemoglobin and of their mixtures has been studied; also the kinetics of their reactions with carbon monoxide. The experiments were carried out both on the chains as they were directly obtained by the preparative procedure, with bound parachloro-mercuribenzoate (i.e. as PMB† compounds) and after removal of the mercurial (i.e. as SH compounds). The oxygen equilibrium of the isolated α or β chains with or without PMB, shows absence of haem-haem interactions, absence of Bohr effect, and high oxygen affinity; the βSH system behaves essentially like haemoglobin H. In contrast, in the oxygen equilibrium of mixtures of the α and β chains, with or without PMB, haem-haem interactions and a Bohr effect are present; the (αSH+βSH) system behaves essentially like normal human haemoglobin. The velocity constant for combination with carbon monoxide of the isolated chains with or without PMB is twentyfold, or more, greater than that of normal human haemoglobin; when α and β chains, with or without PMB, are mixed together, the velocity of combination with carbon monoxide falls to a value similar to that of normal haemoglobin. The absorption spectrum in the Soret region of the deoxy derivative of the isolated chains differs characteristically from that of their mixture, which is the same as that of normal haemoglobin. The results indicate that the functional interactions in haemoglobin require the simultaneous presence of the two kinds of polypeptide chain, α and β.
ASJC Scopus subject areas
- Molecular Biology