A NOVEL COMPLEX FORMED BETWEEN THE FLAVIVIRUS-E AND NS1 PROTEINS - ANALYSIS OF ITS STRUCTURE AND FUNCTION

We examined the structural features and functional significance of a n ovel complex which forms between the envelope (E) protein and nonstruc tural protein NS1 of Murray Valley encephalitis (MVE) virus. Western b lot analysis of virus-infected C6/36 cell lysates revealed that the un denatured form of this E-NS I complex was a heat-sensitive E-(NS1 dime r) complex. Furthermore, the E-NS1 complex was observed in cells infec ted with Kunjin, Japanese encephalitis, West-Nile and Kokobera viruses which indicates the complex is a common feature of flavivirus infecti on. E-NS1 complex which had been immunoaffinity purified from MVE-infe cted cell lysates or eluted from gel slices exhibited partial breakdow n into the individual monomers, demonstrating that the complex arose f rom the association of E and NS1 proteins and was not a single polypep tide created from incomplete gene cleavage. Radioimmunoprecipitation a nd western blot analysis of MVE-infected cell lysates and culture flui d preparations collected at various times after infection revealed tha t the E-NS1 complex has a long half life, accumulates in the virus-inf ected cell with time and is not secreted into the extracellular fluid. We have postulated that the E-NS1 complex, or at least a major portio n of the complex, is a non-specific aggregation with no functional sig nificance in the viral life cycle.