Self-assembly of eggplant mosaic virus protein.

Purified bottom component of eggplant mosaic virus (EMV) was dissociated in cold 66% acetic acid in the presence of 0.01 M dithiothreitol (DTT). EMV coat protein free from residual RNA could be obtained by dialysis against 0.02 M sodium acetate buffer, 0.001 M DTT, pH 4.0. The aggregation states of this protein were investigated after dialysis against 0.02 M sodium acetate buffers, 0.001 M DTT, pH 4.0 to 5.5. At pH 4.0, the protein reassembled essentially into threads and small aggregates sedimenting at about 8–9 S. Increasing numbers of isometric shells formed with increasing pH. At pH 5.5, they represented the totality of soluble material and sedimented at about 50 S. Once formed, these shells were stable at pH 7.0, unlike the aggregates formed at pH 4.0, which precipitated if dialyzed directly to pH 7. Conditions required for assembly and some possible implications for the assembly mechanism are discussed.