Fig. 3. Maturation efficiency of wild-type and mutant GHRs. (A) Folding and maturation of wild type (WT) and mutated GHRs transiently transfected in ts20 cells. Cells were pulse labelled for 10 minutes and chased for 15 or 180 minutes (as indicated). Samples were immunoprecipitated with anti-GHR-T and subjected to reducing SDS-PAGE. p, 110-kDa precursor form; m, 130-kDa mature form; A, GHR(C38A-C48A); B, GHR(C83A-C94A); C, GHR(C108A-C122A); AB, AC, BC and ABC are combinations of mutations A,B and/or C. Relative molecular mass standards are shown on the right. (B) Quantification of the maturation efficiencies of the wild-type and mutant receptors. The amount of radioactivity was determined using ImageQuant (Molecular Dynamics). The amount of mature GHR species (130 kDa) was divided by the amount of precursor (110 kDa) and mature GHR species at 180 and 240 minutes chase and represented as a percentage relative to the maturation rate of wtGHR. The values represent the mean ± s.d. of at least two different experiments.