Fig. 6.

The kinetics of alkylation of wild type (a and c) and D3.32N mutant (b and d) M₂ muscarinic receptors by cyclized AChM (a and b) and BR384 (c and d). Homogenates of cells expressing the indicated receptor were incubated with various concentration of the cyclized mustard analogs. The reaction was stopped at the times indicated on the abscissa. [³H]NMS binding was measured in the washed homogenates as described under Materials and Methods. The binding values in the figure are normalized relative to the binding measured in control (untreated) homogenate. The concentration of [³H]NMS was 1 nM. The concentrations of AChM and BR384 refer to the starting concentration of the cyclized mustard analog. The data represent the mean values ± S.E.M. of three to seven experiments, each done in triplicate. The theoretical curves represent the global least-squares fit of eqs. 1 (AChM) and 4 (BR384) to the data.