NRG4 belongs to the neuregulin family and contains 1 EGF-like domain. The protein is low affinity ligand for the ERBB4 tyrosine kinase receptor. It concomitantly recruits ERBB1 and ERBB2 coreceptors, resulting in ligand-stimulated tyrosine phosphorylation and activation of the ERBB receptors. NRG4 does not bind to the ERBB1, ERBB2 and ERBB3 receptors. Recombinant human NRG4 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.