FIG 6.

The 3D structure of the recombinant CsxA crystal is superimposable on that of native exosporium. (A) CsxA density superimposed on that of native exosporium. Surfaces are rendered at a density threshold roughly equivalent to that expected for a 33-kDa monomer. Solid gray represents native exosporium, and yellow mesh represents recombinant CsxA. (B) Projection map of vitreous ice-embedded CsxA crystal at 9-Å resolution. The map is contoured at 0.2 × root mean square (RMS) deviation from the mean density. Solid contours represent density above the mean density; dashed contours represent density below the mean density. The repeating unit is a hexameric ring (dashed circle) of protein density enclosing a less dense cavity. The triangle marks the axis of 3-fold symmetry where rings appear connected. The density for one potential subunit is outlined.