Interaction between hemoglobin subunits in the hemoglobin . haptoglobin complex.

The accessibility of hemoglobin sulfhydryl groups to modification by p-mercuribenzoate @"B) was tested in order to investigate the effect of the hemoglobinhaptoglobin association on the contact between a and /3 chain subunits. Previous evidence indicates that a molecule of tetrameric hemoglobin binds to haptoglobin as two separate a& dimers. Modification of the hemoglobin a and B chain sullhydryl groups (al04, P93, and p112) by p-MB prevents the formation of a, /3 hemoglobin dimers; nevertheless, a combined mixture of