Figure 4.

σNS undergoes a hexamer-to-octamer transition upon binding RNA. (A and B) SAXS-derived ab initio models of hexameric σNS and σNS–RNP complex. Twenty best models for each σNS apoprotein species (A) and σNS–RNP (B) were generated as described in ‘Materials and Methods’ section, averaged using DAMAVER (light mesh) and filtered using DAMFILT (superimposed dark surface). (C) CCS of σNS oligomers detected by ESI-IMS-MS. σNS apoprotein species are shown in blue and σNS–RNP are shown in red. Dashed horizontal lines denote CCS values estimated for the SAXS models of σNS apoprotein and the RNP complex, shown in (A) and (B), respectively. Masses of each oligomer and their charge states are summarized in Supplementary Tables S4 and 5.