The pore is completely plugged towards its periplasmic end, though, by the presence of a large 150-residue N-terminal domain, which consists mainly of a four-stranded β-sheet. Two loops from this ...

The superposition of the structures of PRAI and IGPS revealed several striking differences at the ends of the barrels formed by the C-termini of the β-sheets (Fig. 2): IGPS has an N-terminal ...