The Epstein-Barr virus-determined nuclear antigen: a previously identified 48K component and higher-molecular-weight forms of the antigen are structurally related.

The Epstein-Barr virus(EBV)-determined nuclear antigen (EBNA) was purified from a variety of EBV-carrying nonproducer cells. Antigen was detected by Western blotting and subsequent visualization of complexes with antiserum/protein A. All cell lines contained several EBNA components, ranging in molecular weight from 48,000 (48K) to 73K. Even higher-molecular-weight forms of EBNA-positive immunoreactivity were detected, but in much lower yield and in only some preparations (81K in Raji; 120K in Namalva and Raji). Preparations in which the 48K, 65K, 70K, or 73K polypeptides predominated had amino acid compositions with largely similar distributions for most residues. The preparations also yielded similarly sized large fragments upon proteolytic treatments. These findings suggested that all structures are related and that the 48K component may be a part of, or a degradation product from, the larger 65-73K components.