Structural Superimposition

Abstact

ZYG11B is a substrate specificity factor for the cullin-2-RING ubiquitin ligase (CRL2), which plays a critical role in the recognition and degradation of Gly/N-degrons. Yet, how ZYG11B assembles with CRL2, and how ZYG11B couples specific substrate recognition to CRL2-mediated ubiquitination, is unknown. We present the cryo-electron microscopy (cryo-EM) structures of the CRL2(ZYG11B) holoenzyme alone and in complex with a Gly/N-peptide from the inflammasome-forming pathogen sensor NLRP1. The structures indicate that ZYG11B folds into a leucine-rich repeat followed by two armadillo repeat domains that promote assembly with CRL2 and specific recognition of the NLRP1 Gly/N-degron that is revealed by viral protease cleavage. Our structural and functional data indicate that blocking ZYG11B recognition of the NLRP1 Gly/N-degron inhibits NLRP1 inflammasome activation by a viral protease. Overall, we show how the CRL2(ZYG11B) E3 ligase complex recognizes Gly/N-degron substrates, including those that are involved in viral protease-mediated activation of the NLRP1 inflammasome.