DOK proteins are enzymatically inert adaptor or scaffolding proteins. They provide a docking platform for the assembly of multimolecular signaling complexes. DOK4 functions in RET-mediated neurite outgrowth and plays a positive role in activation of the MAP kinase pathway. This protein is putative link with downstream effectors of RET in neuronal differentiation. DOK4 may be involved in the regulation of the immune response induced by T-cells. Recombinant human DOK4 protein, fused to His-tag at N-terminus, was expressed in E.coli.