In vitro assembly of bovine rotavirus nucleocapsid protein.

The nucleocapsid protein (VP6) of bovine rotavirus was purified from in vitro-derived single shelled particles by CaCl2 or LiCl treatment. The protein exhibits polymorphism. Specifically, hexamers and small hexagonal lattices were present in many of the samples. Tubular particles formed between pH 5.0 and 9.0 were moderately stable to changes in temperature and ionic strength and were shown to be composed of nucleocapsid protein. Their formation is fully reversible. Spherical particles resembling single-shelled virus formed at pH 4.0. A novel structure in the form of sheets composed of a small-hole lattice formed in samples shifted from pH 6.0 to 4.0. The results demonstrate the importance of the nucleocapsid protein and of protein-protein interactions for rotavirus assembly.