Figure 5. Solution structures of S. acidocaldarius FlaI with and without ATP.

(A) Experimental scattering profiles are shown for wt FlaI (lower curve) and for the Walker B mutant FlaI^E336A in the presence of ATP and MgCl₂ (upper curve). The theoretical scattering from A. fulgidus GspE is shown in green for a hexamer and in orange for a monomer. In the presence of ATP and MgCl₂, FlaI forms a hexameric structure similar to the hexameric ring of GspE, without nucleotide this ring falls apart in what seems to be similar to the GspE monomer. Inset: distance distribution functions P(r) of the FlaI hexamer and monomer computed from experimental SAXS data are shown in green and orange respectively. The P(r) functions are normalized to unity at their maxima. (B) Average of 15 ab initio models for FlaI with and without ATP overlaid with the crystal structures of hexameric and monomeric GspE respectively. The model for hexameric FlaI was calculated without and with applied six-fold symmetry in the modelling.