Chemical studies of antibodies and other serum gamma globulins

1. Eight immune rabbit ?-globulins and three abnormal human myeloma ?-globulins have been characterized by electrophoretic and ultracentrifugal studies. 2. Eight specific pneumococcal polysaccharide-rabbit antibody precipitates as well as normal and hyperimmune rabbit- ?-globulins were prepared. 3. The 2, 4-dinitroflurobenzene technique described by Sanger was used to determine the free amino groups of several rabbit, human, bovine and equine serum globulin preparations. All the rabbit ?-globulins possess one N-terminal alanine residue and 70 lysine residues. DNP-aspartic acid isolated from every hydrolysate of DNP-rabbit ?-globulin suggests the presence of a labile bond involving the amino group of an aspartyl residue. Human ?-globulin II-1, 2 has one N-terminal aspartic acid residue and two N-terminal glutamic acid residues; human ?-globulin II-3, one aspartic and one glutamic acid as N-terminal residues. These findings suggest that human ?-globulin is a mixture of several different proteins, some composed of two or more polypeptide chains. The two ?-globulins isolated from the sera of multiple myeloma patients each has two N-terminal glutamic acids. The lysine content of these proteins, however, differs. A purified cryoglobulin has approximately 1.5 moles each of N-terminal aspartic and glutamic acid residues indicating that it also is a mixture of at least two ?-globulins. The hydrolysates of DNP-derivatives of bovine and equine serum globulins as well as a specifically precipitated equine antibody contained several DNP-amino acids each present in less that a molar quantity. This suggest that bovine and equine serum globulin like human ?-globulin is a mixture of many proteins which differ in the nature of their N-terminal residues. 4. The N-terminal sequence of amino acid residues in four specific rabbit antibodies was determined by methods described by Sanger and Porter. The sequence alanylleucylvalylaspartylglutamyl which occurs in rabbit antiovalbumin and normal rabbit ?-globulin occurs in each of these antibodies suggesting that only one species of ?-globulin is produced by the rabbit. 5. Amino acids are hydrolyzed from human and rabbit ?-globulins by carboxy-peptidase. These proteins, therefore, apparently have one or more free ?-carboxyl groups. 6. The amino acid composition of four rabbit antibodies and two human myeloma ?-globulins has been determined mainly by chromatography of hydrolysates of the proteins of columns of Dowex 50. No difference in the composition of the rabbit antibodies was found. The abnormal human ?-globulins differ significantly from each other and from normal human ?-globulin, 7. The significance of these data has been discussed in terms of the current theories of antibody formation.