Figure 2.

Type I receptor amino acids 482–492 are critical for down-regulation. Down-regulation assays were performed on clones expressing a full-length chimeric type II TGF-βR and either a full-length chimeric type I receptor (▴; A105) or type I receptors truncated after amino acid 216 (▵; Δ216), 441 (□; Δ441), 481 (▪; Δ481), 492 (○; Δ492), or 498 (●; Δ498) as described in MATERIALS AND METHODS. Percentage of control binding is calculated as the percentage of zero time (no prior GM-CSF treatment) specific binding. The data represent the mean ± SE of three independent clones assayed three times for the truncated receptors and five times for the A105 cells, all in duplicate.