Regulatory part that prevents formation of the Nlrp1b inflammasome: in absence of pathogens and other damage-associated signals, interacts with the C-terminal part of Nlrp1b (NACHT, LRR and PYD domains-containing protein 1b, C-terminus), preventing activation of the Nlrp1b inflammasome. In response to pathogen-associated signals, this part is ubiquitinated by the N-end rule pathway and degraded by the proteasome, releasing the cleaved C-terminal part of the protein, which polymerizes and forms the Nlrp1b inflammasome