FIGURE 1.

Competition binding curves of glycosylated IGF-II isoforms to purified extracellular domains of IGF-IR (A) or IR-A (B). Increasing amounts of each ligand were incubated in complex with 25 ng of purified receptor and 100,000 counts of Eu-IGF-II. Complexes were trapped on antibody-coated plates, and the time resolved fluorescence (TRF) was measured. The results are expressed as percentages of the TRF measured for Eu-IGF-II·receptor complex in the absence of competitor and are expressed as the means ± S.E. ■, IGF-II; □, glycosylated 1–156; ▴, glycosylated 1–104; ▵, glycosylated 1–87.