What is the structure of the nuclear pore complex?

The main components of the nuclear pore complex include: 

Columnar subunits – Columnar subunits are integral proteins that make up the major portion of the nuclear pore complex. They traverse the nuclear membrane. 

Ring subunits – Appearing as circular structures, ring subunits make up the outer and inner boundaries of the nuclear pore complex against the membrane. 

Annular subunits – Annular subunits occur in a radial arrangement in the nuclear pore complex. 

Luminal subunits – Luminal subunits occur between the 2 layers of the double membrane. They help to keep the nuclear pore complex anchored to the nuclear membrane. 

Fibrils – Fibrils extend into the cytoplasm as filaments.