Figure 6.

Detection of cross-linked mutant M3R homodimers present on the cell surface. Intact COS-7 cells expressing the indicated Cys-substituted mutant M3Rs were labeled with the membrane-impermeable biotinlyation agent, sulfo-NHS-S-S-biotin. Membranes prepared from these cells were incubated with 0.5 mM of the chemical cross-linker, BMOE, followed by isolation of biotinylated proteins by streptavidin-agarose, SDS-PAGE (reducing conditions), and immunoblotting with the polyclonal anti-M3 antibody. Asterisk and arrow indicate putative receptor monomers and dimers, respectively. Blot shown is representative of 2 independent experiments.