High affinity insulin binding in the human placenta insulin receptor requires αβ heterodimeric subunit interactions

摘要: Insulin binding to human placenta membranes treated at pH 7.6 or 8.5 in the presence absence of 2.0mm DTT for 5 min, followed by simultaneous removal and adjustment 7.6, displayed curvilinear (heterogeneous) insulin plots when analyzed method Scatchard. However, Triton X-100 solubilization Bio-Gel A-1.5m gel filtration chromatography previously with generated a nearly straight line (homogeneous) Scatchard plot.125I-insulin affinity crosslinking studies coupled demonstrated that alkaline treatment detergent an αβ heterodimeric receptor complex from α2β2 heterotetrameric disulfide-linked state. The ability produce functional was found be time dependent maximal formation preservation tracer occurring min. These data demonstrate (i) combination can result complex. (ii) displays homogeneous binding. (iii) membrane environment maintains association state, which heterogeneous binding, despite reduction critical domains are responsible covalent interaction between heterodimers.