Immunochemical characterization of a mycobacterial antigen designated β

Abstract A mycobacterial antigen called β, earlier demonstrated in ribosomal preparations, has been immunochemically characterized. Heat or alkali treatment destroyed the antigenic activity of β. At acidic pH β formed a precipitate with a protein/RNA ratio of 0.6. An anion exchanger resin adsorbed β at low but not at high ion strength. Trypsin diminished the antigenicity of β, while ribonuclease A seemed to split the β molecule. Dissociation of the protein from the RNA portion destroyed the antigenic activity of β. The results suggested that β is a ribonucleoprotein in which the antigen determinants are distributed on two or more peptides kept together by RNA.