Fig. 3.

The μ2 chain of AP-2 was labeled by the *YQRL peptide containing photoreactive cross-linker in the absence or presence of the competitor peptides (YRSL,ARSL, or YSDN; see Fig. 1). The concentrations of each competitor peptide are indicated in the figure. The YRSL peptide that carries the tyrosine-based motif interfered with the cross-linking reaction between the *YQRL peptide and the μ2 chain when the YRSL peptide was presented at a concentration as low as 10 μm. Both the ARSL and YSDNpeptides lacking the motif failed to interfere with the cross-linking reaction at concentrations up to 1 mm.