Characterization of a high-affinity and specific binding site for Gas6

We have purified a novel growth-potentiating factor and demonstrated that tie factor is coded by the gas6 gene. Moreover, we have suggested the presence of a Gas6 receptor on rat vascular smooth muscle cells. In this study, we further analyzed the binding of Gas6 to its receptor. Tissue and cellular distribution of the binding; activity of I-125-labeled Gas6 showed that the binding site existed in many but a limited range of tissues and cell types. Further characterization of the binding of [T-125]Gas6 using HOS cells demonstrated that the specific binding was dependent on the presence of Ca2+. Chemical cross-linking of [I-125]Gas6 to HOS cells resulted in the formation of a high-molecular-mass complex, suggesting the presence of a high-molecular-weight receptor.