Extended Data Fig. 8 |. The ZU5 domain and DPP9 sterically hinder UPA polymerization.

a, Modelling of a FIIND polymer using the observed UPA^A-UPA^B relationship. Adjacent ZU5 molecules would clash, suggesting that UPA polymerization cannot occur in complete FIIND. b, Modelled recruitment of free UPA adjacent to UPA^A and UPA^B in the ternary complex with DPP9. The additional UPA subdomain next to FIND^A clashes with the ZU5 subdomain, and the additional UPA next to UPA^B clashes with both DPP9 monomers in the complex, suggesting that DPP9 inhibits UPA oligomerization. c, A modelled UPA oligomer based on the near front-to-back interaction in the NLRP1-DPP9 ternary complex. In the model, the N-terminal tails of free UPAs are shown in either the UPA^A (pink) or UPA^B (magenta) conformation in complex with DPP9, but in reality, this conformation is likely to be different. d, Modelling of a UPA oligomer formed on one side of a FIIND^A-CT^B complex. The NLRP1-FIIND^A-NLRP1-CT^B binary complex can polymerize with freed NLRP1-CT. a-d, DPP9 is coloured in green, and NLRP1 domains are coloured as indicated.