Figure 3.

Agonist-dependent formation of disulfide cross-linked homodimers between mutant M3Rs containing the R260C point mutation. Membranes prepared from COS-7 cells expressing the R260C mutant M3R were incubated with 100 μM Cu-Phen in the absence or presence of the indicated concentrations of carbachol. Membrane extracts were then subjected to SDS-PAGE under nonreducing conditions, and receptors were visualized via Western blotting analysis using the polyclonal anti-M3R antibody. Asterisk and arrow indicate putative receptor monomers and dimers, respectively. Two additional blots gave similar results.