We have purified a novel growth-potentiating factor and demonstrated that the 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 125I-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 [121I]Gas6 using HOS cells demonstrated that the specific binding was dependent on the presence of Ca2+. Chemical cross-linking of [125I]]Gas6 to HOS cells resulted in the formation of a high-molecular-mass complex, suggesting the presence of a high-molecular-weight receptor.
