Co-immunoprecipitation of Tir and CK18. (A) Western blots and IP/western blots of membrane extracts of Δtir- and WT EPEC-infected HeLa cells: lanes 1 and 2 are Δtir- and WT-infected extracts, respectively, detected with anti-CK18; lanes 3–5 are IP/western blots detected with anti-Tir, where lane 3 is a WT-infected extract first IP with preimmune serum and lanes 4 and 5 are Δtir- and WT-infected extracts, respectively, IP with anti-CK18; lanes 6 and 7 are western blots of Δtir- and WT-infected extracts, respectively, detected with anti-Tir. Tir was specifically co-IP with the CK18 antibodies. (B) Western blot of membrane and cytoplasmic extracts of Δtir- and WT EPEC-infected HeLa cells detected with anti-CK18: lanes 1, 2 and 5, 6 represent cytoplasmic extracts, and lanes 3, 4 and 7, 8 are membrane extracts of Δtir (lanes 1, 3, 5 and 7)- and WT (lanes 2, 4, 6 and 8)-infected HeLa cells. Lanes 5–8 were first IP with anti-Tir. CK18 was specifically co-IP with the Tir antiserum. (C) Western blots of membrane and cytoplasmic extracts of Δtir- and WT EPEC-infected HeLa cells detected with anti-CK8. Lanes 1, 3, 5 and 7 represent membrane extracts and lanes 2, 4, 6 and 8 are cytoplasmic extracts of Δtir (lanes 3, 4, 7 and 8)- and WT (lanes 1, 2, 5 and 6)-infected HeLa cells. Lanes 5–8 were first IP with anti-Tir. A higher molecular weight form, at approximately 97 kDa, of CK8 was co-IP with the Tir antiserum. (D) Western blots of membrane and cytoplasmic extracts of Δtir- and WT EPEC-infected HeLa cells detected with anti-actin. Lanes 1, 3, 5 and 7 represent membrane extracts and lanes 2, 4, 6 and 8 are cytoplasmic extracts of Δtir (lanes 3, 4, 7 and 8)- and WT (lanes 1, 2, 5 and 6)-infected HeLa cells. Lanes 5–8 were first IP with anti-Tir. Monomeric actin was specifically co-IP with the Tir antiserum.