title: Ultrastructural analysis of the membrane insertion of domain 3 of streptolysin O.
abstract: Streptolysin O (SLO) is a membrane-damaging toxic protein produced by group A streptococci. We performed an ultrastructural analysis of pore formation and the mechanism of hemolysis by SLO, using a mutant form of SLO [SLO(C/A)-SS] and native SLO. SLO(C/A)-SS was unable to penetrate the erythrocyte membrane as a consequence of immobilization that was due to a disulfide bond between domains. The SLO(C/A)-SS molecules that bound to membranes formed numerous single-layered ring-shaped structures that did not result in pores on the membranes. These structures were similar to the structures formed by native SLO at 0 degrees C. After treatment with dithiothreitol, SLO(C/A)-SS that had bound to membranes formed double-layered rings with pores on the membranes, as does native SLO at room temperature. Our morphological evidence demonstrates that an increase in temperature is necessary for the occurrence of conformational changes and for the formation of double-layered rings after the insertion of domain 3 into the host cell membrane. On the basis of a model of the oligomeric structure of SLO, we propose some new details of the mechanism of hemolysis by SLO.
authors: Laboratory of Electron Microscopy, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan. sekiyak@pharm.kitasato-u.ac.jp
authors: Kachiko
authors: K
authors: Sekiya
authors: Takumi
authors: T
authors: Akagi
authors: Kiyoko
authors: K
authors: Tatsuta
authors: Eriko
authors: E
authors: Sakakura
authors: Tsutomu
authors: T
authors: Hashikawa
authors: Akio
authors: A
authors: Abe
authors: Hideaki
authors: H
authors: Nagamune
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000648:ultrastructure; D002462:Cell Membrane / Q000737:chemistry* / Q000648:ultrastructure; D004912:Erythrocytes / Q000737:chemistry* / Q000648:ultrastructure; D006801:Humans; D046032:Microscopy, Energy-Filtering Transmission Electron; D008954:Models, Biological; D011817:Rabbits; D013301:Streptolysins / Q000737:chemistry* / Q000235:genetics; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D013301:Streptolysins; C025964:streptolysin O