Fig. 1. Bcr is bound by the first PDZ domain of PDZK1. (A) GST fusion proteins with each of the four PDZ domains of PDZK1 immobilized on glutathione-Sepharose beads and incubated with lysates from Calu-3 cells. Bound products were eluted, separated by SDS-PAGE and visualized with Coomassie Blue staining. (B) The peptide masses of the trypsinized major band pulled down with PDZ 1 (marked with arrows in A) identified by MALDI-TOF mass spectrometry. The peptides identified were distributed over the entire Bcr protein. (C) Bcr in several human epithelial cell lines. Lysates from human epithelial cells were separated by SDS-PAGE and Bcr was detected by western blotting using the C20 anti-Bcr antibody.