Figure 2.

Mapping of molecular domains at the neuromuscular junction using immunogold labeling. Immunogold particles that label specific synaptic proteins were mapped at neuromuscular junctions. A–C, E, Representative micrographs of the immunogold labeling (circled in red) of UNC-13 (A), UNC-10/Rim (B), DYN-1/dynamin (C), and UNC-49/GABA_A receptor (E). D, The distribution of membrane-associated gold particles relative to the nearest dense projection, measured as the distance along the plasma membrane (dDP-M). Each circle represents an individual measurement. The median value is indicated with a line. The presynaptic proteins UNC-13 and UNC-10/Rim are predominantly localized near dense projections, whereas dynamin is distributed laterally. To illustrate the distribution of a protein intimately associated with dense projections, the previously published SYD-2 immunogold labeling data set (Yeh et al., 2005) was reanalyzed using the outlined mapping strategy and plotted. F, Distribution of UNC-49-associated gold particles. Distances were measured from gold particles to the line perpendicular to the plasma membrane below the dense projection (dDP-Post) (see Fig. 1B).