To verify the predicted M2/Cav-1 binding, pull-down as well as co-immunoprecipitation experiments were carried out. For pull-down experiments, biotinylated peptides carrying the putative CBD of M2 or a mutant CBD with alanines instead of the motif's core aromatic residues were incubated with cell lysates and complexes were processed as specified in Material and Methods (Fig. 5A) .