ABSTRACT

The α-macroglobulins are multifunctional proteins which bind divalent metal ions such as zinc and nickel, bind many cytokines, and modulate the immune response and the inflammatory reaction. The necessity of an organism having large quantities of proteinase inhibitors present during the acute phase reaction, to prevent widespread tissue destruction, has been appreciated for the last decade or more. The polypeptide chains of each of these proteins have regions shared in common which are important for the various activities identified for these proteins. The organization of the subunit polypeptide chain into the mature circulating active protein differs somewhat for each of the rat α-macroglobulins. The presence of an internal thiol ester bond in these proteins is a unique characteristic of this family of proteins. Proteinase inhibitors make up a major fraction of the plasma proteins in vertebrate species.