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Figure 5
The model of stressosome assembly. (a) Envelope structure of the RsbRA–RsbS complex determined under a nonsymmetric restraint at 9.1 Å resolution (C1 envelope). The model of the STAS icosahedron and the crystal structure of the RsbRA N-domain (PDB entry 2bnl; Murray et al., 2005BB33) were superposed onto the icosahedral core and protrusions of the C1 envelope, respectively. The position of the RsbRA STAS domains was determined based on the protrusions corresponding to the RsbRA N-domain. The STAS domains of RsbRA and RsbS and the RsbRA N-domain are colored green, purple and yellow, respectively. (b, c) Ribbon diagram (b) and cartoon (c) showing the organization of the STAS domains in the stressosome core. (d, e) Two distinctive binding interfaces between RsbRA and RsbS (interface A and interface B) are indicated by the red and blue boxes in (c). The model of the stressosome core was superposed onto the STAS icosahedron which comprises 60 RsbS monomers to show the difference in interaction between RsbS–RsbS and RsbRA–RsbS. Interface A and interface B are shown in (d) and (e), respectively. RsbRA and RsbS are colored green and purple, respectively. Polar residues of RsbRA at the binding interface that is not conserved between RsbRA and RsbS are drawn as green stick models and labeled. (f) GST pulldown of RsbS. Cell lysates (upper panel) that contain GST-RsbS and RsbRA (native or mutants) were prepared and loaded onto GST resin. Proteins bound to the resin were eluted and confirmed by SDS–PAGE (lower panel). The interaction between RsbRA and RsbS was decreased by R189A and R189A/Q191A mutations in RsbRA. * indicates the positions of the R189A and R189A/Q191A mutants of RsbRA on the SDS–PAGE.

IUCrJ
Volume 6| Part 5| September 2019| Pages 938-947
ISSN: 2052-2525
https://doi.org/10.1107/S205225251900945X