Acetylation of Amino Groups and Its Effect on the Conformation and Immunological Activity of Ovalbumin*

A procedure is described for the specific acetylation of the lysine residues of ovalbumin. Six acetylated ovalbumins varying in the degree of modification from 21 to 98% were prepared and were found to be homogeneous by polyacrylamide gel electrophoresis, immunodiffusion, and immunoelectrophoresis. As expected, the anodic movement of ovalbumin increased and the isoionic point shifted to lower pH values with progressive acetylation of the protein. Measurements on ultraviolet absorption, fluorescence, tryptic digestion, intrinsic viscosity, gel filtration behavior, and immunological reactivity demonstrated that the native folded conformation of ovalbumin was appreciably altered by acetylation. However, even the maximally modified ovalbumin retained considerable residual structure consisting of regions of ordered structure containing antigenic determinants.