At 4°C transferrin bound to receptors on the reticulocyte plasma membrane, and at 37°C receptor-mediated endocytosis of transferrin occurred. Uptake at 37°C exceeded binding at 4°C by 2.5-fold and saturated after 20-30 min. During uptake at 37°C, bound transferrin was internalized into a trypsin-resistant space. Read Full Publication (PDF)