Crystallization of the avian reovirus double-stranded RNA-binding and core protein sigmaA

Abstract

The avian reovirus protein sigmaA plays a dual role: it is a structural protein forming part of the transcriptionally active core, but it has also been implicated in the resistance of the virus to interferon by strongly binding double-stranded RNA and thus inhibiting the double-stranded RNA-dependent protein kinase. The sigmaA protein has been crystallized from solutions containing ammonium sulfate at pH values around 6. Crystals belonging to space group P1, with unit-cell parameters a = 103.2, b = 129.9, c = 144.0 A, alpha = 93.8, beta = 105.1, gamma = 98.2 degrees were grown and a complete data set has been collected to 2.3 A resolution. The self-rotation function suggests that sigmaA may form symmetric arrangements in the crystals.

Figure 1

Crystals of the avian reovirus σA protein. (a) A typical crystallization drop containing multiple small crystals. (b) A single large crystal; this crystal is about 0.3 mm in width and 0.05 mm thick.

Figure 2

Self-rotation function calculated using the program MOLREP (Vagin & Teplyakov, 2000 ▶) from a complete σA data set. (a) χ = 180° section; (b) χ = 50° section, indicating the presence of multiple noncrystallographic twofolds and a single noncrystallographic higher symmetry axis.