| Abstract: | An ice nucleation-active strain of Erwinia uredovora shed vesicles when cultured at low temperature (l0?C). We isolated an ice nucleation-active vesicle fraction from the culture medium by ultrafiltration, ultracentrifugation, and gel filtration. Western blot analysis showed that this cell-free vesicle fraction contained an ice nucleation-active protein (InaU). The process of the InaU transport to a shed vesicle was examined by immunohistochemical analysis using electron microscopy. The examination showed the following successive processes: InaU molecules first assemble around the inner membrane, then the assembly enters a vesicle justforming on the surface of the outer membrane, and finally the vesicle, 100–400 nm in diameter, leaves the surface to be shed with InaU molecules occluded. |
