The conformation of an atypical IgG myeloma protein and its papain fragments

Abstract

An immunoglobulin IgG (Sackfield) which is known to have polypeptide chains shorter than those of typical proteins of its class has been subjected to fragmentation by papain in the presence of cysteine. One fragment was recovered which was indistinguishable from normal Fc fragment. The other fragment was related to normal Fab fragment but differed from it in several of its properties. The molecular weight was only one-half that of normal Fab. The optical rotatory dispersion spectrum of IgG (Sackfield) had features which differed from those of typical IgG myeloma proteins. The optical rotatory dispersion spectrum of Fc (Sackfield) was identical with those of other myeloma proteins, while the Fab (Sackfield) spectrum reflected the differences observed in the parent protein.