Fig. 2. Transport motifs bind to COPII components in vitro. Peptides comprising the sequence of ERGIC-53 tail with the indicated C-terminal motifs were coupled to thiol-activated Sepharose. The beads were incubated with detergent lysates of HepG2 cells. Bound proteins were separated by SDS-PAGE, and nitrocellulose blots were probed for COPII binding using antibodies against COPII subunits. (A) A binding assay with peptides bearing double substitutions at XX position. (B) A binding assay with peptides bearing single motifs. Lane C: lysate corresponding to one quarter of the amount incubated with peptide beads. Representative examples of at least three independent experiments are shown.