ID2 belongs to the inhibitor of DNA binding (ID) family, members of which are transcriptional regulators that contain a helix-loop-helix (HLH) domain but not a basic domain. Members of the ID family inhibit the functions of basic helix-loop-helix transcription factors in a dominant-negative manner by suppressing their heterodimerization partners through the HLH domains. This protein may play a role in negatively regulating cell differentiation. Recombinant human ID2 protein, fused to His-tag at N-terminus, was expressed in E.coli.