ENZYMATICALLY PRODUCED SUBUNITS OF PROTEINS FORMED BY PLASMA CELLS IN MICE

Abstract

The relationship of Bence Jones protein (mol. wt. = 45,000) to a [beta]2A myeloma protein (mol. wt. = 160,000) formed by the same mouse plasma cell tumor (MPC-2) was investigated. The [beta]2A myeloma protein was split by treatment with papain and cysteine into fragments (S20 w = 3.7S), similar in size to the Bence Jones protein (s20,w = 3.6S). Two types of fragments with distinct antigenic groupings designated S and F, were present in the MPC-2 myeloma protein digest. The Bence Jones protein was found to share antigenic determinants with S fragments from the MPC -2 [beta]2A myeloma protein and with S fragments from gamma globulins. Physicochemical observations indicated, hosever, that the Bence Jones protein was not identical to the globulin fragments products by treatment with papain and cysteine. Comparison of the S and F fragments from [beta]2A and gamma globulins revealed that the antigenic features shared by the various globulins derived from plasma cells (gamma and [beta]2A myeloma proteins, the range of normal gamma globulins) are largely properties of the S fragments, whereas the distinctive antigenic differences between the gamma and [beta]2A myeloma proteins were properties which appeared in the F fragments of the molecules.