CRYSTALLIZATION AND PRELIMINARY-X-RAY ANALYSIS OF ROTAVIRUS PROTEIN VP6

As a first step to gain insight into the structure of the rotavirus vi rion at atomic resolution, we report here the expression, purification , and crystallization of recombinant rotavirus protein VP6. This prote in has the property of polymerizing in the form of tubular structures in solution which have hindered crystallization thus far. Using a comb ination of electron microscopy and small-angle X-ray scattering, we fo und that addition of Ca2+ at concentrations higher than 100 mM results in depolymerization of the tubes, leading to an essentially monodispe rse solution of trimeric VP6 even at high protein concentrations (high er than 10 mg/ml), thereby enabling us to search for crystallization c onditions. We have thus obtained crystals of VP6 which diffract to bet ter than 2.4 Angstrom resolution and belong to the cubic space group P 4(1)32 with a cell dimension a of 160 Angstrom. The crystals contain a trimer of VP6 lying along the diagonal of the cubic unit cell, result ing in one VP6 monomer per asymmetric unit and a solvent content of ro ughly 70%.