PURIFICATION OF IPAC, A PROTEIN INVOLVED IN ENTRY OF SHIGELLA-FLEXNERI INTO EPITHELIAL-CELLS AND CHARACTERIZATION OF ITS INTERACTION WITH LIPID-MEMBRANES

Entry of Shigella flexneri into epithelial cells and lysis of the phag osome involve the secreted IpaA-D proteins. A complex containing IpaC and IpaB is able to promote uptake of inert particles by epithelial ce lls. This suggested that Ipa proteins, either individually or as a com plex, might interact,vith the cell membrane. We have purified IpaC and demonstrated its interaction with lipid vesicles. This interaction is modulated by the pH, which might be relevant to the dual role of Ipa proteins, in induction of membrane ruffles upon entry and lysis of the endosome membrane thereafter.