Interpretation of the 10 Å rotation function of the satellite tobacco necrosis virus

The rotation function calculated with 10 Å three-dimensional data from monoclinic crystals of the satellite tobacco necrosis virus was fitted numerically to an icosahedral axis set. The r.m.s. angular deviation of the observed peak maxima from the calculated model axis set was 0.67° and the largest deviation was 1.4°. Thus, there is no significant deviation from icosahedral symmetry at 10 Å resolution. An investigation of the effects of the data inclusion limits and the radius of integration on the resolution of neighboring peaks in the rotation function showed that the best resolution was obtained by using only a thin shell of the highest-resolution data available and a radius of integration no larger than the estimated diameter of the virus protein subunit.