First steps towards structural insights into the active NLRP3 inflammasome have been taken: We have determined the directionality of ASC PYD filament growth on NLRP3 PYD nucleation seeds! In a tedious titration experiment, Inga succeeded in elongating ASC-mCherry filaments on preformed NLRP3 PYD seeds. Surprisingly, they grow on only one side for the existing filament. We determined the NLRP3 PYD filament structure, which exhibits a characteristic sawtooth silhouette in electron micrographs. This feature helped to identify the B-end as the growing direction of the filament.
