Acidic domain of the phosphoprotein (P) of vesicular stomatitis virus differentially interacts with homologous and heterologous nucleocapsid protein (N).

The homologous and heterologous interactions between the nucleocapsid protein N and the phosphoprotein P of New Jersey and Indiana serotypes of vesicular stomatitis virus were studied. SP6 derived N and P mRNAs were cotranslated in rabbit reticulocyte lysate and the complexes formed thereof were analyzed by 7.5% nondenaturing polyacrylamide gel electrophoresis. P protein of VSV(NJ) has two binding sites for homologous N protein: One located within the C-terminal 11 amino acids (within domain III) is responsible for the formation of five specific complexes while the other site, which spans the acidic domain I, is necessary for the formation of the sixth complex only. In contrast, P(IND) does not form the sixth complex when interacted with homologous N protein. Interestingly, P(NJ) forms only complexes 1 to 5 when it interacts with N(IND). The above results suggest that the complex 6 formation or domain I interacting site is NJ-serotype specific. Two chimeric P proteins were made using heterologous domains I and II/III of the P proteins of both serotypes. The soluble interaction of the chimeric proteins with the N protein supported the observed serotype specific interactions. The chimeric P proteins bound with equal efficiency with N-RNA template of both serotypes. These results strongly suggest that the acidic domain I of the P protein differentially interacts with homologous and heterologous N proteins. The biological significance of these findings is discussed.