[Mechanism of pore formation on erythrocyte membrane by streptolysin-O]

The erythrocyte membrane damaged by streptolysin-O (SLO) was observed in negative staining electron microscopy. It was confirmed that rings took arc (c-ring), sigmoidal (s-ring) or circular (o-ring) structures, and had electron-dense centers of a diameter of 24 nm and 4.9 nm width. We found a crown structure on top of the ring in view of side projection. The ring structure was constructed by three layers of the electron lucent top which was the crown, the second dark layer, and the third, base part which embedded in the erythrocyte membrane, and the heights were 3.2, 1.6, 5.0 nm, respectively. When the ghost membrane of erythrocyte was treated with SLO, the double of the inner and outer layers of a ring were observed by the negative-staining images. The figures of rings taken by under focus showed that one ring might be constituted between the 22 and 24 pair of inner and outer molecules. Totally 44 or 48 toxin molecules might be required for one O-ring.