Macroglobulin structure: homology of mu and gamma heavy chains of human immunoglobulins

The amino acid sequence of fragments obtained by cyanogen bromide cleavage of the mu-chain of a human gammaM-globulin is homologous to the NH(2)-terminal sequences of the gamma-chain of human and rabbit gammaG-globulins and is related to that of human light chains. This supports the hypothesis that light and heavy chains evolved from a common ancestral gene.