Intermediates in the reassociation of reduced haptoglobin.

Oxidative reassociation of alpha and beta subunits of human and equine haptoglobins as well as of two 2 alpha . 2 beta tetrameric hybrids made of subunits of each haptoglobin was studied following reduction of interchain disulphide bridges and also with isolated, PHMB-protected subunits in homologous and heterologous systems. Molecular mass and subunit composition of the intermediates appearing in the process of successive oxidation of -SH groups were determined by SDS-polyacrylamide-gel electrophoresis. The yield of subunit reassociation into homologous and heterologous tetramers 2 alpha . 2 beta was very high (75-80%) and the reassociated haptoglobins exhibited properties of native proteins in binding reactions with haemoglobin and with specific antibodies.