Structure of the T9SS PorKN ring complex reveals conformational plasticity based on the repurposed FGE fold.

ABSTRACT: The type IX secretion system (T9SS) is a protein secretion machinery unique to the Bacteroidetes-Chlorobi-Fibrobacteres superphylum, which plays crucial roles in bacterial pathogenesis and gliding motility. It is composed of >15 proteins, including the proton-motive force-dependent PorLM motor, the PorKN ring anchored to the outer membrane, and the Sov translocon. Here, we present the cryo-electron microscopy (EM) structure of the PorKN ring complex from Porphyromonas gingivalis at 3.2 Å resolution. Our structural analysis reveals that PorK contains a repurposed formylglycine-generating enzyme-like fold, which serves as a structural hub for complex assembly rather than enzymatic activity. The complex exhibits a 33-fold symmetry with PorK and PorN assembling two tightly packed and we

SUBMITTER: Liu X 

PROVIDER: S-EPMC12421860 | biostudies-literature | 2025 Sep

REPOSITORIES: biostudies-literature