Further Studies on the Amino Acid Composition of Immune Proteins

Although the protein nature of antibodies is now firmly established, there is little available information concerning their amino acid composition. Studies recently reported from this laboratory have provided methods of isolation which have made available sufficient amounts of immune proteins for analytical study (l-3). These proteins are for the most part electrophoretically homogeneous, but are not completely homogeneous in the ultracentrifuge (2). Moreover, the limitation should be recognized that these proteins were all isolated by physicochemical methods, and not by immunologically specific precipitation. Each protein fraction, therefore, includes a considerable portion of material which is not immunologically specific. Brand, Kassell, and Saidel (4) and Brand (5) have already reported analyses on a r-globulin preparation from human plasma. A previous paper from this laboratory (Smith, Greene, and Bartner (6)) has dealt with the content of carbohydrate and of several amino acids of the immune proteins which have been isolated from human, horse, and bovine plasma, and with the immune lactoglobulins of the cow. The present paper presents analyses on this group of proteins for seven additional amino acids.